May C

@ElisaAnne21 The J18 has been awesome! It is the perfect size for my level of production as a hobbyist. It easily gets to the temperature I need (cone 6). I've fired it 15 times in the last 11 months (of which 2 firings had problems - see below). 
One thing I really like is that because it's so old, the technology is relatively straightforward. Recently, two of the infinite switches on the controller failed. It took a few firings that tripped the kiln sitter faster than expected for me to realize that rather than cycling the elements on and off, they were on full-blast at any position of the dial other than 0. With some super helpful advice and encouragement from @neilestrick , I bought replacement switches on eBay and swapped out the old ones. With the new switches, I realized that when someone says "two hours on low" it can mean very different things for different kilns!  I have to turn the new switches to "3" (which is almost at "M") to be roughly equivalent to "Lo" on the original switches. 
I continually fantasize about buying a digital controller, but I am holding off because I appreciate that the kiln's manual everything forces me (a beginner who had previously never fired a kiln) to pay attention to the different choices I make and how they affect the outcomes.
Would love to hear how your kiln works out!

IMO
I think they would be fine certainly to try, it’s not as if this element is gonna fly out of there. We have elements grow out several inches from kilns with worse slots  after many firings  and we just torch them back into place neatly. Plenty of internet videos on doing that. I would try it out and I believe it will not be a whole bunch of trouble. If my thought is wrong or if you discover they are worn it only  means you will simply need to replace your elements sooner than later. This could be a good opportunity to get all your parts.
I like your center pin best . Not sure I would need more than two of those about 1/3 of the way in from each end. You could always take a long straight pin and rotate it in far enough so it’s embedded in the brick and catches behind the top of the element holder.   In my experience the element holders on those kilns allow elements to grow and shrink pretty uniformly. Pinning it firmly at one point often inhibits this movement and causes more trouble with unequal growth. I would be more concerned the pins are imbeded towards the center of the brick and not out towards the face so you do not damage the outside  face of the brick.  My experience, I have pinned far worse.

If they're in the brick far enough to hold solid they will work. I don't have confidence in the two coming from the top, though. If you want to make a guard rail, I would try straightening out the staples so they're nice and long, and put a series of straight pins all along there, as that will give you more metal into the bricks.