Ailing rooster - please help

Hello:

This is going to be long, so please bear with me. We have a Black Jersey Giant Rooster (8 months old) who has been ill for a couple of weeks. Initially, we noticed that he was walking with his head not fully extended, neck feathers fluffed. He was eating, drinking. staying with flock, just walking funny. I found him upside down, unable to right himself about a week ago and brought him into the house. At that point his crop felt full, but he did not want to eat or drink. His vent was surrounded with poop, so I cleaned that up. His (same breed) father and one other hen (as 3-4 week old babes) showed signs most similar to wry neck. We consulted a vet who thought the problem was neurological and suggest a vitamin (I don't recall which) supplement. We used diluted Poly-Vi-Sol, provided wax worms and both chicks survived and have shown no further sign of wry neck (or any illness for that matter).

He appears to have signs of wry neck, so we have been using Ploy-Vi-Sol in his water. However, most notable is the gurgling (sounds like a a human's stomach growling) noise he makes when we give him water. We hold it under his beak and he drinks, though I do not think he's drinking as much as he needs. Second most notable was I heard him fart last week (who knew a chicken could fart?).

I was reading the wealth of info here yesterday and sounds like this could be several things. He is eating (offering non-GMO feed, black oil sunflower seeds, dried meal worms), and we make sure he drinks. We offer water laced with Poly-Vi-Sol, plain water, and I bought him Pedialyte yesterday (not sure how to use this). He is pooping, but very little. His comb and wattles are dull, he spends much of his time lying down, and if stressed, shows signs of wry-neck again. He's not preening, of vocalizing other than to cluck if I pick him up.

Our small flock consists of about 24 hens and 3 roosters. Both roos are sons of the original Roo. They are free-range birds, who get non-GMO or organic feed. They have 3 connected but separate roosts, and we have never seen the roosters fight. We live in northern Indiana, so it's cold here, which is another reason he is in the house.

He may be feeling better as he caught a moth out of the air yesterday, but we sure would like to help him heal faster. Thanks in advance ... any progress he's making is very slow.