If he's turning back to his original color, that's good. However, I recommend that you don't use Bettafix or anything that ends in the word -fix because there's an ingredient in there that can damage their labyrinth organ, and we don't want that. Some other fish medication would be better, such as Seachem Kanaplex.
You should go back to changing the water 50% once a week. It's recommended in OldFishLady's water change recommendations (sticky in this section of the forum). http://www.bettafish.com/showthread.php?t=115758
What brand of fish food are you feeding him? Don't forget to fast him once a week! :)
But overall, it seems like you're doing a pretty good job. Good luck with your boy!