What's wrong with my Dwarf Gourami?

There really isn't too much else you can do except keeping his water clean and correctly administering the medication. The spazzy zipping could be due to ich or it could just be because he's in pain. Being transported to a fish store is a lot of stress on a fish and then being bullied adds to that. I would continue treating for the fin rot and hope for the best. If you start adding even more meds to the tank with the state he is in now the chemicals may kill him. Your fish would not have survived in Walmart and you've done your best so don't feel bad whatever happens. Just keep the tank clean and hope for the best.