From the sounds of it, this really isn't the right time for you. This boy seems like a decent enough guy, and you seem to connect with him well enough. It's just... you have too much going on right now in your relationship life. You might just be on some form of rebound, y'know, like you said, wanting someone you can't have.
Here's my advice: after you end your current relationship, wait a while, maybe a week or two or however long it usually takes you, to let yourself calm down. Make sure not to push the boy too far away or bring him too close, which I guess you're kinda doing now. If you're still attracted to this boy after waiting, then it's genuine. You could also spend this recuperating time getting to know him a bit more to make it clearer whether you like him or not.
Anyway, that's my spiel. Good luck. : )