If your BF/roommate is willing to try, why not ask the people point blank (nicely) if they happen to be looking for a home for their kitty? That you find him in the hall a lot, and maybe he's a bit more of a handful than they expected sort of thing.

Also, a friend of mine had her daughter staying with her temporarily, and the daughter had a cat. My friend was quite allergic. However, the daughter found some stuff at the pet store - a liquid or something that you put on the cat. It keeps the dander down and makes kitty less allergenic. It worked great for my friend.

Good luck - and thanks for caring for the baby.