I don't listen to Taylor Swift. To be blunt, why would you get back in a relationship with a guy who treated you badly? I don't think you should get engaged, let alone get married. First, you resent his treatment of you. That is fair, but who wants to start of an engagement with someone they resent? Who wants to get engaged to a person you feel like you're "settling" with. Honestly, you should do him and yourself a favor by breaking up and moving on. I think the resentment and feelings that you settled will cause issues down the road. If you're not in love, end it and find a guy you're excited to marry.
This. And, none of us know if you're with him because you're 'settling' or because you are (to quote a PP) 'in familiar'.