Min

Copying a design versus using the same technique while making a pot are two different things. Are there any new designs in functional ware that haven't been done before by someone somewhere, I don't know but I sort of doubt it.
I have noticed quite a few makers doing exactly what you describe; leaving the mark of the making process visible at the joins. I don't think you need to waste your energy trying to justify your work. Getting inspiration from others work is one way to challenge yourself into making new forms, and making them your own.  I'm sorry you are going through this, it must have been upsetting to you.

Hi and welcome to the forum.
From Standard's website and their  Lowfire Slip page there is a link with glaze recommendations. Duncan IN1001 "slightly yellow, may blur crisp underglaze lines". There are four other Mayco glaze result descriptions there also. It seems the least yellowing recommendation is Spectrum 700. Standard recommends doing both bisque and glaze to cone 04.
Link here: https://cdn.shopify.com/s/files/1/0039/8177/0841/files/105-LFW_Glaze_Rec.pdf?v=1674848426

Hi and welcome to the forum.
From Standard's website and their  Lowfire Slip page there is a link with glaze recommendations. Duncan IN1001 "slightly yellow, may blur crisp underglaze lines". There are four other Mayco glaze result descriptions there also. It seems the least yellowing recommendation is Spectrum 700. Standard recommends doing both bisque and glaze to cone 04.
Link here: https://cdn.shopify.com/s/files/1/0039/8177/0841/files/105-LFW_Glaze_Rec.pdf?v=1674848426

Slow. Both for firing up and cooling down.
These pictures are from Digitalfire of lowfire ware, pots have cracked from uneven cooling, edges will have cooled faster than the middle area of the pieces. The way to avoid this is to have the cooling down go as evenly as possible. Slow the cooling down between 1150F - 950F, I go at 100F/hour through this zone with suspect work.

 There is negligible shrinkage, ie less than 1% between bone dry greenware and bisque firing to ^06- ^04, would be interesting to see data that shows refiring to a lower temp causes more shrinkage.
edit: when having your piece in the kiln put it between shelves, not at the top or bottom of the kiln, this helps the heat even out also. I put rectangular or triangular kiln posts around the outside edge of the shelf also. (round posts can roll)
 

Copying a design versus using the same technique while making a pot are two different things. Are there any new designs in functional ware that haven't been done before by someone somewhere, I don't know but I sort of doubt it.
I have noticed quite a few makers doing exactly what you describe; leaving the mark of the making process visible at the joins. I don't think you need to waste your energy trying to justify your work. Getting inspiration from others work is one way to challenge yourself into making new forms, and making them your own.  I'm sorry you are going through this, it must have been upsetting to you.

This. 100000X this. If your clay body is giving pinholes of some kind with several glazes, it’s the clay body, not the glaze or the assorted firing cycles. It may well be that an ingredient in the Laguna body just doesn’t want to play nice, whatever is done with it. You have to weigh wether you like using this clay more than you want a perfectly defect free surface.
If you need a good red clay/white glaze combo, M390 and Ravenscrag slip 80/20  with frit 3134, and 2 opacifiers of your choice. (I recommend a tin and zircopax combo if you don’t want any titanium variegation). Reasoning: they give different qualities of white. Tin by itself is very soft, and can be grey-ish or even drift towards a violet in certain light when used on M390 in particular. It’s also expensive. Zircopax by itself is very stark, and gives a very “bathroom fixture” white that resists breaking or pooling. The 2 together give a soft white without weird tonal casts, gives a little more visual interest and offsets the end price of the glaze. I use a max of 10% opacifier, but judging from the look of your photos, you might want a slightly more translucent version, so you could see what happens with 7 or 8%. 
I fire with a very analog kiln at home, so I can’t give specific numbers on ramps and speed. I slow my kiln down around the carbon burnout stages mentioned in the Steve Davis article, and I judge that through the colour of the kiln. I’ve recently started working at a place that has brand new Bartlett 2 touchscreens though. I feel spoiled! They are to be preferred over my methods.
I think speed of bisque is more important than end temperature, so slow through the appropriate zones. I think the Naomi Clement one is a bit of overkill.  The 12-14 hours of Davis’s cycle (assuming no drying soak at the beginning) is plenty long. Note the pauses around 1500F that both Clement and Hulk have suggested.
The glaze cycle I use to get what is effectively cone 7 is a drop and hold, similar to what you’ve already worked out. I go to cone 6 with a 20 minute hold after the drop.
Note that there will be upcoming changes to M390: according to my supplier, Plainsman demand has gone through the roof lately, and they’re struggling to keep up. They have one clay mixer that they have to cycle all their different clay bodies through from lightest to darkest. While another one has been ordered, it’s not expected in until next year. In the meantime, they’ve made the decision to remove the 80 mesh sieve from the machinery in order to get the clay to go through faster. This will affect M390’s texture starting this year. So we’ll all have to revise some porosity testing until they get the new machinery in place.
 
The last suggestion I would have is another bisque cycle. But this time, only go to 010. There have been a few reliable potters in various internet spaces lately speaking about this (For Flux Sake podcast in particular). I believe the argument is that the application a more porous clay body gives a dipped glaze results in fewer defects. I haven’t experimented with this personally though, so that one is a shot in the dark if nothing else works.

Tagging @Callie Beller Diesel on this in case I'm misremembering but I believe she fires 390 to cone 7 for absorption reasons.

I have attempted to contact Laguna twice before about a different clay (Laguna 65) and received a reply that they were forwarding my question to someone else -- never heard back.   So I probably won't contact them again.  
I recently purchased a box of M390 and threw some test bowls.  I am including them in my next series of tests to see what the results are -- figured if Tony had success on M390 with the glaze G 3806 that I could use that as a comparison for the results on the Laguna 613 and go from there.  He uses the C6DHSC firing schedule so if I don't have good results on the  M390 it will indicate that something else is going on that I haven't thought about.   As part of covering all the bases I'm bisquing a few bowls at ^02 for comparison. Going to give the Laguna clay about another 2 weeks to reveal its mysteries then abandon ship (I only have 6 bags left).   -- 6 more glaze  firings to go (the golf course is calling!)  
The good thing is that I am really good at throwing test bowls now.    

Loosely related

 

750 ml yogurt container, so I guess that would be nearly as small as the paint cups with the handle. It sits in the splash tray (Bailey wheel), don't keep any sponges or chamois in it. I start with warm water then top it up as the day goes along. After a few throwing days I put it to one side, stir a splash or two of peroxide and then it goes into the reclaim.  3 yogurt containers used in rotation. 

FTL message usually indicates not enough power to get to temp. Worn element(s), bad relay - some mechanical or electrical reason it cannot maintain a reasonable rate of heating at the end. On the test tile side, Orton says most of the important (flux) heat work work will be done in the last 200-250f degrees given a reasonable rate of rise during this period. If your kiln stops well short of that last 200-250 degrees then generally things can be restarted as if nothing significant happened. 
In your case, you are sort of close so restarting likely fine if you can make temp at a reasonable rate. If it stalls again though you are going to need to diagnose the problem and those tiles are likely half baked and depending on the stall temp can end up looking any number of ways. If you have witness cones in place then plus one - you will have an idea of how much heatwork you achieved. If virtually none, then repair the kiln and refine.
My guess is it stalled for a reason and It will stall again. My rule of thumb is if it stops 250f or more before it’s final temp it usually can be cooled and refired after repairs with it likely ending up looking / firing as normal. In effect no heatwork was done during the most important phase.

750 ml yogurt container, so I guess that would be nearly as small as the paint cups with the handle. It sits in the splash tray (Bailey wheel), don't keep any sponges or chamois in it. I start with warm water then top it up as the day goes along. After a few throwing days I put it to one side, stir a splash or two of peroxide and then it goes into the reclaim.  3 yogurt containers used in rotation. 

Spent some time chatting with Susan Dolan at NCECA this past weekend. First of all, she’s lovely, and cares deeply about creating quality tools. She was extraordinarily helpful in guiding me to which tools would work best for me and my work.  She knows it’s hard to get her tools, but she’s literally a one woman show. Her focus is so much on making, she chose not to have a booth and was set up with Clay Planet. Fortunately, she brought some pieces with her, and I was able to pick up 8 new tools (Lucky me!).  I don’t know if she had stock left over at the end of the show, but I’d look at Clay Planet first to see if they have any stock.  I don’t think Dolan is selling from their website, but prefer for a select group of distributors to manage that end so they can keep the focus on making. Hope that helps!! 

Hi Hannah and welcome to the forum.
I've never used ash from domestic waste but your post has made me curious. I did a quick google search and found a fair bit of info on Municipal solid waste ash. From one study the main components found in it were Si, Al, Fe, Mg, Ca, K, Na, Cl, SiO2, Al2O3, CaO, Fe2O3, Na2O, K2O. But also found in the fly ash were the heavy metals, "Cr, Cu, Hg, Ni, Cd, Zn and Pb are the most commonly found in MSWI ash, and Zn and Pb usually exist in the largest amounts (fly ash and bottom ash..."
For a comparison a general generic analysis of wood ash from Hamer and  Hamer would be  8 Na2O, 17 K2O, 12 MgO, 27 CaO, 1 Al2O3, 24 SiO2, 7 P2O5, 4 Fe2O3
The heavy metals lead, cadmium and mercury found in domestic waste ash testing done in the link (below) I pulled this info from would be an area of concern. 
https://www.mdpi.com/2071-1050/2/7/1943

I think that since so many of us fire to midrange the go to mindset is bisque low, fire higher to glaze. Problem with this when working with earthenware is more often than not the commercial glazes are rated in the 06-04 range yet many earthenware bodies will actually mature higher than this and still be porous enough to take glaze well. I haven't used the body in question, but if it can go to 02 (as the lit suggests) then I would at least try 03 and see how it does. 

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

Hi Hannah and welcome to the forum.
I've never used ash from domestic waste but your post has made me curious. I did a quick google search and found a fair bit of info on Municipal solid waste ash. From one study the main components found in it were Si, Al, Fe, Mg, Ca, K, Na, Cl, SiO2, Al2O3, CaO, Fe2O3, Na2O, K2O. But also found in the fly ash were the heavy metals, "Cr, Cu, Hg, Ni, Cd, Zn and Pb are the most commonly found in MSWI ash, and Zn and Pb usually exist in the largest amounts (fly ash and bottom ash..."
For a comparison a general generic analysis of wood ash from Hamer and  Hamer would be  8 Na2O, 17 K2O, 12 MgO, 27 CaO, 1 Al2O3, 24 SiO2, 7 P2O5, 4 Fe2O3
The heavy metals lead, cadmium and mercury found in domestic waste ash testing done in the link (below) I pulled this info from would be an area of concern. 
https://www.mdpi.com/2071-1050/2/7/1943

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

I looked up the Mass Red clay from Sheffield Pottery, from their info it fires from 06 up to 02. I don't use commercial glazes so I also looked up the glazes you are using, Mayco Elements have a range from ^06 up to ^6 and the opalescent are ^05 if you go at 270F and hour for the final 200F of firing and the Artist's Choice recommend ^05. 
All claybodies are strongest when fired to their top maturity temp/cone. So for your body the clay needs a higher bisque than what your glazes fire to. This is okay for earthenware as the body will still be porous enough to accept the glaze well. I would suggest bisque firing to ^02 and turning the dial up very slowly. Don't rush when you turn it up! Leave  peeps open to get air through the kiln, it helps burn off impurities in the clay. I would suggest leaving all the peepholes open until you see the kiln glowing red inside then shut the bottom one and leave the top one open for the entire firing. Once the kiln stops then you can close the top one off. (I'm assuming it has 2 peepholes?)
For the glaze firing, again you want to slow it down, doesn't have to go as slow as the bisque though. I'm not familiar with your kiln but what you are trying to do is slow down the firing, Try and stretch out the middle and then particularly the end of the firing. Someone more familiar with your kiln than I am should be able to help you with this part. 
Given that the clay has already reached it's maturity with the bisque firing then the glaze firing is to get the best looking glazes you can. Cone 05 should do it although the Mayco Elements can go higher, if you have a hotter area in your kiln you could try putting those glazes there. When I looked at some images of Mayco Elements I do see a fair number of pinholes in one of them when fired to ^06 so the odd one might be more prone to pinholes. (image below from Mayco's website of Oyster Shell)
 
 

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

For sure you can get the chem to match using silica + calcium carb for wollastonite. I've done the reverse with recipes calling for calcium carb and subbed in wollastonite and reducing the silica in the recipe so the formulas match. What I found was the wollastonite versions melted noticeably more.  Some recipes won't show a difference, depends on glaze mobility and how much CaO is involved. I think another factor is the mesh size of the silica being used in the recipes. Perhaps very fine silica, ie 90 micron compared to 45 micron would show a difference in the melt if used with calcium carb? I've always thought of wollastonite as being like a frit, albeit a lumpy one, it melts really well and with minimal LOI.

For sure you can get the chem to match using silica + calcium carb for wollastonite. I've done the reverse with recipes calling for calcium carb and subbed in wollastonite and reducing the silica in the recipe so the formulas match. What I found was the wollastonite versions melted noticeably more.  Some recipes won't show a difference, depends on glaze mobility and how much CaO is involved. I think another factor is the mesh size of the silica being used in the recipes. Perhaps very fine silica, ie 90 micron compared to 45 micron would show a difference in the melt if used with calcium carb? I've always thought of wollastonite as being like a frit, albeit a lumpy one, it melts really well and with minimal LOI.

Is this the commercial Amaco  Wash you are using? If it is I would try brushing it on the wiping it back with a damp sponge to remain in the recesses then apply a glaze over top. I think leaving it without wiping it back would be too intense. Whatever glaze you use will dilute the intensity of the Amaco Wash.
 

I guess it would depend on whether the data on Glazy is the same as someones current material analysis (garbage in garbage out). Materials data fields vary between sources.

Is the glaze coming off during the firing and landing on the kiln shelf? If that is the case, it can be due to the way the wet glaze dries and cracks and falls off.
If the glaze is not falling off onto the shelves, but is leaving bare spots, that can be a different cause.
I can't tell which is happening from the description or photos.