I've never had much luck with ghost shrimp. I got some shipped to me once. All of them were missing limbs because they just attacked each other the whole time. Not only that, but they didn't last long. They were the only things in the tank and still were gone within a week.
Just so you know, once scuds are introduced to a tank, they're near impossible to get rid of. I had them in my 75 gallon. Broke it down, emptied it out and started over. Scuds manages to get back in. Not sure if it was on plants or anything else. But like i said, they're really hard to...
Most of the LFS's in my area never have a detailed species description for crayfish. It'll just say "blue lobster" or something like that.
Just be careful as they can get relatively big in a short period of time. I bought one once and had to give it back to the store a few months later...
I always assumed that fish with that bent spine/TB look, that it had to do with inbreeding or poor genetics. I agree with jpappy789. Feed it well and keep an eye on it to see if it improves.