Hi Kailey! I'm so sorry to hear about your rooster. He's a pretty brave fellow!
Incase this can help, I had a cull rooster that was attacked in our barn late last fall. My rooster had wedged himself between a square bale and the sliding door of the barn. He was in shock and chilled when I found him in the morning. His tail feathers were gone and he had wounds along his neck (bite marks I assume) He also couldn't lift his head or neck at all, his head rested on the floor in front of him...he couldn't keep his head up like your rooster.
I couldn't keep him in the house, he was kept in a kennel in our closed rooster shed. My rooster couldn't peck or eat anything, the only thing he could do was drink. I gave him an electrolyte vitamin mixture in a water dish and helped him with his neck to drink it exactly the same way you did in your post #30.
It took 2.5 weeks before he could begin to lift his head. As soon as he could control his head a bit I fed him chick starter in a dish and held him while he pecked at it. He progressed well from there and was soon eating on his own. He's healed 100% and is back to normal.
Unfortunately, I was injured at the same time so I needed assistance to get him out of his kennel and I was only able to help him drink him a couple times a day. He rested the remainder of the day and was not handled. I put one of his cull buddies in with him that had an injured eye. I did not wash his wounds, they were done bleeding and had clotted so I left them alone. I kept an eye on the wounds for infection.
It was a lot of work with him but I couldn't put him down after he'd managed to survive the attack. I'm glad I didn't give up on him.
It may take some perseverance with your rooster. But as long as your rooster doesn't give up, I think you have a good chance of him responding and getting well. He looks much better and more alert than my guy did. The fact he has his head up while sitting in the box is a good sign.