You have felt hurt and your reaction was to deliver it back in a variety of forms. But he seemed unaffected and now you are even angrier and freezing him out isn't giving you the satisfaction you want. SO you feel stuck with what to do next it seems.
If you truly have a desire to know the "truth", you will need to be open and non-confrontational and he will have to be open and secure enough to discuss it with you honestly. I admit it seems unlikely that such an atmosphere can be cultured based on the history you have outlined, and neither of you really know each other well enough for it to easily happen. I am not condoning his behavior at all, but you too have sent many mixed signals along the way rather than just talking to him frankly.
BUT, if you want to "clear the air" for your own sake, that's reason enough to approach him and try to talk. Own your own feelings and use lots of "I" statements ("I felt" or "I noticed" etc.) rather than "You did this" or "You were a jerk" ... you need to resist the urge to "hurt him back".
I think Amargith's explanations are a great place to settle if you decide not to talk to him.
But I think you really need to explore why you care so much at this point, why you are feeling the way you do. I suspect it's because you don't just want closure, you want a bit of revenge too ...