We live on a 11 acre off grid property and we make fires quite often, to make charcoal, to cook in our fire pit (which is where the pottery was made) and to dispose of things that can't be composted etc. so that won't be a problem. I couldn't imagine living in the sort of setting you describe, seems really restrictive.
We went through with the firing, we used a mixture of activated charcoal, salt, manure from the horses and the sheep and iron oxide that had collected under my sander from years of sanding rust off of things. Turned out real nice but they did weep water a little bit, the solution we used was shellac (the pure stuff that comes from a lac bug, not synthetic stuff) which is apparently perfectly food safe as long as the medium used to dissolve it is pure ethanol and not methylated spirits, we added 3 coats to the inside of each vessel, one coat all around the outsides (to avoid them getting too shiny) and another three coats to the bottom, shellac is water resistant not water tight, but one coat can hold back water for 4 hours, so I think they should be fine for nearly everything, I'm drinking tea out of one of the cups right now without any leaking, even less so than my store bought cups which leave little water rings.