Here are the treatments for Swim Bladder Disease as posted by our wonderful vet student DarkMoon17:
Swim Bladder Disease (SBD)/Bloat
•Symptoms: Betta has trouble swimming, maybe he can’t stay upright and can only swim on his side.
•Treatment: This is not a contagious or fatal illness. If it isn’t congenital (aka a condition that he/she has had since birth), then it is caused by over feeding or feeding the wrong foods. Bettas will typically recover after a day or two of Epsom Salt treatments (1-2tsp/gal) and fasting. You can help prevent a reoccurrence by switching to a better pellet food, feeding less and offering a more varied diet. To make it easier for the betta to eat and breath, you can make the water shallower. You can offer him/her frozen daphnia (sold at Petsmart) as daphnia will help him/her pass stool. DO NOT FEED THEM PEAS.
I'm not sure why it is so bad to feed them peas...but the concensus on here is that they are not good for the bettas. Hopefully someone else can chime in on why they are bad...I believe it has something to do with bloat? I can't remember for certain.
As for the fin rot, the treatment for that is either OTC antibiotics, or Aquarium salt (different from epsom salt). I think that if you treat him for the SBD, then the epsom salt would most likely help his fin rot as well. The two different salts work differently, but rot is a bacterial infection, and that's going to be susceptible to being killed off by any salt, epsom or aquarium.
For more disease information, check out these links:
I hope your guy is feeling better soon!