I haven't updated you guys in a while... He's improving I think. He gets around easier now, puts more weight on that leg, and his foot is straight when he stands on it instead of curling under him. It still looks paralyzed, but it definitely looks like he can use it more than he could before. And the fact that he's standing on it more instead of hanging on the cage bars to take weight off of it is a good sign I think.
As far as the vet telling us to monitor his weight though, I don't know how we're supposed to do that. He doesn't exactly let us catch him, and he's more active now. We also don't have a kitchen scale anymore so we can't measure his weight anyway. But I'm not sure if that will be necessary, since he appears to be improving a lot.