His symptoms sound like Mareks disease to me. Even though he has been top of the pecking order, the others must realize something is off with him, and he senses he needs to hide to protect himself. Can you post a picture of the chicken with the small pinpoint pupil? That sounds like the ocular (eye) form of Mareks.
I would look around to see if you can get a necropsy on your lame rooster if he dies or is culled, just to get a diagnosis. Here is where to contact if you want to get a necropsy or testing:
https://www.uoguelph.ca/ahl/services/necropsy
In the meantime, a chicken sling chair might be made to help him eat and drink, and to get him upright and kept cleaner. Here is a link for that:
https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/
I would look around to see if you can get a necropsy on your lame rooster if he dies or is culled, just to get a diagnosis. Here is where to contact if you want to get a necropsy or testing:
https://www.uoguelph.ca/ahl/services/necropsy
In the meantime, a chicken sling chair might be made to help him eat and drink, and to get him upright and kept cleaner. Here is a link for that:
https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/