I personally think that you are over thinking this, and over medicating, which can be just as hard or harder on a fish that just giving it some time & allowing its own natural immunity to take over.
You've gone from a dewormer, to interpet internal bacteria treatment, to epsom salt infused food, to a medication from Thailand, and now back to another discus medication. Considering that your fish was back to eating with no issues, and acting normal (other than being a bit dark) I think that you would be far better off just leaving him alone & allowing him to gain some strength back. I've never been one to recommend a "shotgun" approach when it comes to medicating fish.