I would recommend getting an API master freshwater testing kit to test your water. You'll want to test daily, then do a 25-50% water change after testing the water. Keep this routine until you get 0 for ammonia and nitrites and 10 or less for nitrates. Treat all water with Prime. This will help him get through cycling his tank.
For healing up his fins, I'd recommend Fish Protector, Vita-Chem and Garlic Guard daily. All 3 can be ordered from
www.thatfishplace.com if you can't find them locally. They will help the healing process for him.
If he has tiny white spots that are like salt crystals, then that could be ich. You'll want to slowly raise the water temp to 83F and keep it there for at least 2 weeks. You can add a product called Ich-Attack to make him feel better, but just the warmer water is the treatment for ich. Normally his water should be 78-80F.
I would recommend feeding him thawed hikari frozen bloodworms - 3 per meal, 2 meals per day. 1 or 2 meals a week could be 3 small pieces (pellet-sized) of thawed & peeled frozen pea.
Hopefully getting him on this schedule will clear up any health issues, get his digestive system going good and get his tank cycled.