Sick MBU puffer

I’ve had this puffer for going on 3-4 years. Live on the coast of the Gulf in US. Did something stupid and fed the puffer some live crabs and shrimp that I’ve caught in the bay. Now he has a swollen jaw that’s been ongoing for several weeks. The jaw mass is so large that it inhibits him from being able to eat normally. Dosed with several different types of antibiotics and nothing has worked. Would appreciate help in solutions. Currently in a holding tank so that I can dose medication. Would love to get community thoughts/suggestions.

Differential ddx includes:

-Bacterial Infection/abscess potentially foreign body from piece of crab shell. Given that it will not respond to antibiotics. I’ve been reading a lot about dropsy. Mostly caused by gram-negative infections. Treated with Augmentin and then Cefipime dosed in his food. (Frozen shrimp) with no improvement. Now dosing the tank with sulfathiazole for about a week. And added aquarium salt dose, 1 tablespoon per 3 gallons, Infection has not progressed, however, it is not improved. Energy levels, however of improved.

-Parasite infection: not an expert in this. I tried paraguard with minimal results.

-Malignancy: based on the acute onset, I do not think that this is the cause.