Whats wrong with my ferret?

I got two ferrets from s good friend yesterday one a girl and one a boy. She got them a couple months ago from someone who said they got them at a pet store and they are both about a year old. The girl is healthy and normal acting but the boy is pretty sick. He does not move around much at all but when he tries he can not use his back legs and drags them around and he walks drunk and falls over and has to rest after a few steps. He also has runny tar black colored poop and is very dehydrated. I have been giving him water threw a syringe which he drinks right up and he seems less dehydrated today then yesterday which is good. He will not eat his food so I was giving him baby enfamil infant formula but I read that can cause him to have the runs worse so I stopped and Im going to start with some ensure later tonight and also try to give him some gerber baby food chicken flavor stage 2 which I read online is good for him when he is sick and something easy I can give in a syringe too. I can not afford a vet right now so I did look things up online and I read about them having low blood sugar a lot and I tried putting the honey on his gums and everything and it did nothing for him so I really do not think it is because of that. Does anyone know what may be wrong with him? and if so what all I can do for him? any help would be great. Thanks!