An update-
Overall behavior has improved - he's more social, and does appear to be injuring himself less when he twitches/flashes. (I'm not sure why - I think the episodes are shorter).
But the twitching/flashing continues...less some days, more others...
I'm at a loss at this point.
The water tests come out ok. I'm doing water changes at least 3x per week with vacueming (that seems to be helping significantly).
I'm not sure the melafix did much - though his mouth does look better as far as redness. The deformity is still there - much of his bottom lip seems to be missing, and though he doesn't appear in pain and he is eating regularly, I'm concerned that the more this goes on the worse it's going to get.
I don't want to consider euthanasia, unless it's absolutely necessary - when he's not twitching he's friendly, generally interactive, and swims well.
I should add I haven't yet been able to find a larger tank that's used, so perhaps that's an issue...but otherwise..any additional ideas?
Thanks-