Most Helpful Guy
Believe it or not, was in the same shoes. And believe me, it was the best choice I ever made. He's depicting the classic phrase: "he wants to have his cake and eat it too". What that means, is that, he wants to do whatever he wants, feel whatever he wants, and still has you. But from your end, that's not okay. It hurts, you feel betrayed, etc.
You should say no to being friends. You should go into no contact, and you should start working on yourself. It'll be hard at first, but over time you'll realize you made the right call. He's just using you as his backup in case other girls fall through. You don't want to be "his backup". Oh hell no.
Your heart will heal, and maybe after awhile, you'll be able to be friends with him. And maybe, after that long while, he'll realize what he lost.
Best of luck, and feel better :)