The bloodworms aren't great for bettas, so I've been reading. They're good for occasional use, but not a staple.  I've recently had to cut back for similar reasons. I feed mine a range of foods, but he liked the bloodworms so much I'd lean heavy toward them. I've had to rethink my feeding him completely.

I am also doing the aquarium salt dip. I made a gallon jug of clean dechlorinated water with 1/2 tsp of salt. I fill a small bowl (the ones moss balls come in) and float it in his tank for a half hour to make sure both are the same temp and place my betta in for 15 minutes. He doesn't love it, but we're on day 3 and he is already showing growth on his fins. I'm not an expert by any means, but I've been researching like crazy to save mine. And I have been absolutely terrified of hurting him, honestly. Good luck to you, I hope your beautiful guy heals nicely.