sorry you lost your discus. Sounds like you did alright though nursing him back health. Has anyone noticed that if you have one discus, it may school with other fish like angels, you could maybe try that.
Other than being sick, he beat the crap out of any other fish that got near him in the LFS tank. The owner was going to freeze him. It was weird to watch, sick black fish hovering on it's side in the tank corner, then turning into a holy terror at the sight of another fish!
After he got out of my QT and into my 35 he killed three cories and a male ram. He just couldn't stand any fish bigger than a tetra. I didn't feel I had the room to put other discus in there anyways, since I would need to add at least three more (two only work if they're paired up, with three one is "odd man out".)