Kitty is FIV/FeLV NEGATIVE!


Now we've got to figure out what is wrong with him and what to do with him

I brought him home with me today since his stray hold was up at the shelter and they are very full and don't really have room for an "unadoptable" cat. I'm hoping to have him for just a week or so until we can find a longer term foster and then hopefully a forever home. I really don't know what to do next. Would like to get him looked at by someone other than the shelter vet who didn't actually do any kind of diagnostic tests and simply did a physical exam. None of us have the money for x-rays and detailed blood tests.
Its strange though, because when I put him in the bathroom and opened the crate, he DID stand up and walk. When he got to the lip of the crate his back legs did kind of drag out behind him, rather than lifting to step over it. He didn't seem to have trouble walking on the floor the few steps it took him to get to the food dish. He does not like his back end touched at all though so I can't really trust their opinion that he's "not in pain". I also noticed that he's very skinny (was wormed, etc. at the shelter so should be ok for that) and that sometimes his eyes move rapidly and repeatedly side to side. No idea on his age, just know that he is a neutered male.
Any ideas, advice, suggestions? Could he have been brain damaged in the tornado?
He's super scared and huddled behind the toilet right now, but I'm hoping he will loosen up a little in a day or two. Unfortunately, I don't have any Feliway or Rescue Remedy and can't get any anytime soon.