More TL;DR progress!
I'm almost done with the first round of Triple Sulfa, just put in the fourth dose. I don't know if this is the right thing to do, but I'm going to discontinue the daily 100% changes.
Fish, while still very healthy in terms of behavior, eating, and swimming, has been worse to his own tail since I started messing with his WC schedule - now almost half of the half that was originally there has been lost to his biting. I caught him swimming in circles for half an hour yesterday just idly chasing and nipping at his tail until I went over and chased him a bit with my finger to get him to stop. ): All his other fins are actually growing out, including the nips in his dorsal - but his tail. He's trimmed it down so much it would make a Plakat jealous.
This is what I've done the last week with Triple Sulfa (mix method):
Day 1 of treatment:
100% change, 1st dose out of four. Lowered the water in his 2.5G to 1G, dosed 1 part sulfa, and 2.5ml Stress Coat (instructions 1ml per gallon). Tail: Fresh damage with some red spots as posted previously.
100% change, 2nd dose after 24 hours as per instructions. 2ml Stress Coat and 1 part sulfa to 1G water. Tail had healed up slightly and red spots had disappeared, but reappeared from new damage during acclimation him back to the WC. Tail chewed a little more than previously.
Removed 25% - 40% of tank water, replaced with equivalent with Stress Coat. Tail healing very slightly; translucent webbing growing back (0.5mm).
100% change, 3rd dose, 1.5 parts Sulfa and 2.5ml Stress Coat to 1.5G. Tail bitten again, only about 1cm between shortest part of tail and Fish's body.
Day 5 (today):
100% change, fourth dose, 1.5 parts Sulfa and 2.5ml Stress Coat to 1.5G.Tail slightly shredded at shortest end (I think that was the furthest he could reach back without breaking his spine). Currently acclimating, ready to go in half an hour. Noticed a little "hole" in his tail maybe 0.1mm big, near the tips where he was biting.
I've noticed that his worst attacks seem to come every time he feels he doesn't have sufficient space to hide (the first time I took out the column decoration, he ate half his tail; took out the five-leafed Java Fern to dose him but put in a 6" silk sword plant instead; he bit his tail, etc).
Along with the second Java Fern mentioned previously, I also picked up a four-leafed Anubias (yeah, crappy, but it was the only one they had and they're forever out of stock), and a little plastic Hermit Crab house
for him to hide in (was the only thing without sharp edges). The Cabomba turned out more trouble than I could handre so I tossed it (dried out, in the garbage bin).
The Hermit House wouldn't stay sunk as I originally suspected, so I've put it sideways in the tank like how I've seen some people do with pots in their Betta tanks, with some of the river rocks weighing it down. The plants come out of quarantine tomorrow after I finish his last 100% WC, then I'll arrange them in his tank so he has plenty of things to hide in while still having swimming room space. I'm thinking of going back to my 50%, 100% WC schedule while keeping up with Stress Coat; the daily changes don't seem to be helping him heal and he healed a lot faster with his pelvic fin rot when I first got him and didn't WC so frequently. Then again, I was using aquarium salt, but I can't use it now since I used it too much before, so idk. :/
Is this a bad idea? I just don't see any improvement...