I'm not sure on the urates/poo but you don't want to house that new guy with your other bps. It doesn't sound like he is very healthy, and you don't want him getting your other snakes sick. He could have parasites. And with the size difference there comes the risk of one injuring the other or even cannibalism. I wouldn't risk putting a male in with your female. If she were to become gravid, since she is too small she could become egg bound, which can be deadly. If you have them all housed separately, I would leave them like that...there are too many risks, especially with the new guy not being in great health.