If you can touch him and he won't move, I'd say he's past the point of no return.
1.0 ammonia is a lot to ask any fish to go through, let alone a fish like a Discus that is increadibly water-quality sencitive. All the symptoms fit, so I'd say it's ammonia poisoning that's got him in this state

Ammonia does permanant damage, so if he is non-responcive totaly, he won't get any better

If he is responcive to touch, he could pull through if the majority of the issue is stress as a result of the burns, but being realitic at this point, I doubt it
For the rest of the fish that have gone through the same thing, it would be a good idea to increase surface agetation and/or airation
All the best
Rabbut