Please read/needing advice!!

I am tangerines mom. He is a 2 year old orange kitty that just had surgery because he could urinate. The name is the surgery is perineal urethrostomy. He has two sisters that he lives with as well. 3 weeks after surgery we are still having problems.
First, he is balding, I mean the hair is coming off like crazy, the vet said that it more than likely is related to stress and the surgery, and he was in the hospital for two weeks.
2nd, his sisters are still hissing at him. They will not come by him at all. They never got along that great to begin with, but this hissing has to stop. I have sprayed the older sister a few times with water.
NOW, Tangerine will not go to the bathroom in the litter box. He goes in the bathtub, he seems to have a hard time urinating, but the vet says he just needs to get used to this new way of going. He's still not himself fully yet. Cannot jump and is not very active. Just need some advice please, I don't really want to bring him back to the vets so soon. I just hope he is just slowly healing.

Ok, I think that he probably does need to go back to the vets. At the very least, ring your vet, ask if this sounds normal or if he should be re-examined.

Second, please stop spraying water at your cats. Despite the fact that it is commonly done, it is not a good idea - you can find more helpful ways of dealing with feline nautiness in the behaviour forum.

Third, it's possible that your cats just don't recognise Tangerine, as he will smell different than he used to after being at the vets. The introduction threads in the behaviour forum will discuss a trick you can do with vaniella (the real stuff, not the artificial kind) which may help.

Fourth, you can try something called Feliway, which is probably available at PetSmart or something, and your vet probably has some as well - it mimics kitty happy pheromones and helps them to relax.

About you baby not using the litter box - he probably remembers it as the place where he was in pain and dosen't want to go back there. Try and provide him with a brand new one. Also since he goes in the tub - I would definately have him re-examined maybe he has a urinary track infection.