Sadly, I think the answer to that is pretty obvious. If he really wanted to be with you, he would be. Or at least he wouldn't be getting involved with his ex again with all the complications.
But most importantly, I don't think it makes any sense for you to even consider getting back with the guy. He's currently dating his ex after telling her he loves her while he was going out with you. Who cares if it was a dare? It was disrespectful to you. And he's back with her either way.
So I think you should file your experience with him in your 'life lessons' archive, and look for someone new.