You’d be amazed at what one tiny spot can do to impact feeling/pain elsewhere in your foot. If that’s the spot and you provide some space in the tongue I’m guessing that you’ll end up with a tremendous amount of relief, though it sounds as though you’re crunching the medial nerve that runs through the same area. Again, one little spot could cause the pain and numbness you’re experiencing.
On a side note about heating... conventional oven = bad, bad, bad. Same deal with direct immersion in hot water. The potential for sole warp with the oven and the accelerated oxidation of plastic when directly immersed in hot water are both big issues.
I’m not referring to specialty ovens that are intended to be used with specially formulated plastics (and plug boots don’t fall into this category), but even those can involve a plate system to maintain sole integrity. The hot water bath can be used in conjunction with a basting bag, but with a plug boot the wall thickness is such that you a) can typically get what you need without stretching and b) have to take your time to get a stretch to work. And regardless, it really sounds like you have an easy-to-fix, non-shell issue.
