Well, that's a difficult situation.
Obviously having been with him so long, its going to take more than two months to adjust to a platonic friendship, and because of this your feelings of betrayl/jealousy etc are perfectly natural.
It sounds like you have a very valid reason for breaking up with him, one which may save a lot of heartache in the future, but since it doesn't sound like a mutual break up, then as others have said, it is unsurprising he would want to make you jealous, in an attempt to get over you if you like.
Someone said it was unfair of him to mess you around, however if he actively made it clear he wanted to get back together with you, and you said no, then, in his mind, he was clear what the situation between you two was and therefore he felt able to kiss this other girl.
Obviously I understand why you'd be upset, but I'm sure he'd only have lied to spare your feelings, I'm sure you wouldn't have preferred if he'd told you all the details, every message they sent to each other etc.
I can certainly see where you're coming from, but it's not fair to be angry at him, when as a young single guy, he was merely doing what young single guys do.
You seem fairly certain a relationship in the future isn't possible, therefore as hard as its going to be, you're going to have to accept that he's going to move on. He can't mope around and pine for you forever, and I'm sure you won't do so either. If you find this too difficult at the moment, maybe it's time to step back from the friendship and evaluate what you really want!
Hope it all works out.