Talk about a tough call!!! There is one option that is not listed .... is it even a possibility to just release him back like he is? Is he in terrible pain? I know cats are very tough and often seem to "heal" themselves. In the wild, they manage will all sorts of things and overcome them. As long as you know he is healthy .... not spreading disease or making kittens, then maybe just leave the hip alone?

edit : or what about amputation of that leg? Would that be less expensive for you? There are many "tripods" out there doing great!