Thank you all very much. I went to the pet store and they talked about getting this spray called Comfort Zone, which has the pheromones that are supposed to relax him but I'm super tight on money. He has an open litter box so I could try a closed one.
On top of all this my roomies are really stressing on putting the litter box where they had it with the last roomies of their's-- in the fireplace. I was here a few times while the previous roomies lived here and their cats had no problem going potty while it was in the fireplace. I tried it and all the sounds coming in through the chimney freaked out Zuko. Trying to find another place for it. I hate locking him up in the bathroom with it.
Also-- when he does it in the litter box he just leaves it uncovered. When he goes on the floor he tries and tries to cover it up. He just paws at the floor trying to hide it. It's just so sad seeing him go from world's greatest cat when it comes to using the litter box to him just refusing it. I wish I had never gotten that other cat. He's still healing up, has scabs all over, and is missing patches of hair from where she really got him.