Aw! You are being very kind hearted to be taking care of the injured kitten. But, it is not happy or a good life for him to live inside a cage like this one. I understand why you don't want to let him out, and I know tom fights can be deadly, especially to such a fragile kind of cat. I am sure he couldn't defend himself.
Do you have a spare stall (yeah, the rarest thing in existence when it comes to minis!)? Or can you have him neutured? The tom may not see him as a threat if he were fixed?
When I was a teenager, we had a cat who I named Duran (urgh), but as a kitten, she accidentally got slammed in the outside heavy door. She had water on her brain and was not expected to live and walked drunk. But, she did recover (over a couple week period). But, she was never really "right" in the head. She got the new name "Crazy". You could pet her and she'd be purring then she would snap and attack you. If she got in the house, she'd end up under the bed growling and snarling like a mountain lion.
Amazingly, this couple that lived in our neighborhood sort of took her in not knowing she had a home. We think she started going to their property to hunt. Somehow, our family figured out that couple was taking her in, feeding her, etc. So, we shared her. The wife was so attached to Crazy (I think they called her Samantha). When they would go away, WE would go to their house to feed her the Fancy Feast they gave her. Of all the pets my family had, that someone would fall in love with crazy Crazy was pretty amazing. That couple had to move to the other coast, and of course, we let them take their crazy Samantha with them.
So, they can recover but it sounds like given the amount of time, this kitten will be as he is for now on...
If you can get him to a vet, there may be things that could be done. Once one of my shih-tzu's started walking in circles and falling over. Naturally, it happened late evening after the vet was closed. She had been acting depressed for a few days but is ultra sensitive. We had gotten a new bed and I thought that had disturbed her (with her, that would be logical). I was so sick to death worried for Willow, but it turned out the only thing wrong with her was an ear infection. She had to stay at the vet a few days to be treated, but recovered fine.