The white patches have gone away!!! YAY!
His eye still looks a little swollen but again hasn't gotten any worse.
I don't use BetaFix by API. I have a different treatment that I believe is called BettaMax. It's blue and comes in a little fishy-shaped dropper bottle. I can't seem to find it online to make sure thats actually the name and I threw out the label because I know the dosing instructions by heart and I live in a dorm room - anything that takes up unnecessary space has to go. I was told by the guy I bought it from that he uses it on all the Bettas in the store whenever they show signs of any bacterial or fungal illness and it works 99% of the time. It seems to be working for whatever was growing on my fishy's back, too.
I plan on going to my local pet store (a family owned store, not a chain. The people there are really passionate about animals and the guy in the fish department is very knowledgeable. If your fish doesn't get better with the treatment they give you, you can bring a sample of water in and they will test it for you!) and see what they have to say as soon as the roads here open up again.
Thank you everybody again for your help.