He doesn't want a relationship.
But he wants the physical part of a relationship.
And what is it you want from this?
You do not seem you want just a slice of the pie, but you want the whole thing, good and bad, but unfortunately you're not getting it here.

I'd seriously find someone else and invest your time and efforts into and who will return them as well. Grad school is hard enough as it is, not to mention relationships shouldn't be that complicated =)

Good Luck =)