That's good that he is more lively. I would still try VERY hard to get Hill's Prescription Diet a/d from the vet. It will be easier on his system and he will get more from it than he will the Ensure. Ensure has lactose I believe, which may be a bit hard on his digestive system.

For a stuck shed, soak him in a small tub with lid(shoebox or smaller) that has lukewarm water that reaches about mid-body on his sides. Put snakey in tub, put tub with lid on inside enclosure on warm side, and leave him for an hour. You can do this once daily until the shed is removed. Concentrate on the tip of the tail, eyecaps and any shed that is encircling his body. If there are patches still stuck, but they aren't described by any of the above, then leave them until his next shed. They will come off then.

Have you bumped up his enclosure temps a bit? I remember them being a little on the cool side, especially that warm spot.

Congrats for getting him going. I don't know too many people with your patience and determination.