Gaining

Depending on how extreme his kink is, but yeah I'd say you should request something a little heftier. Even if it's relatively small.

Impossible to make a judgement on the worth of a trade without knowing both ends of the deal.

Well, based on his current stats, and since he's gained a significant amount already, maybe you let it go & he'll gain another 15+ pounds anyway. But since it seems you like this guy, just go with his requirement, it could be really good for you both.

Go for 250 a nice number