If you already feel that you're "settling" with this bf than you'll probably regret it the longer it goes on. "Settling" doesn't mean happiness. It means safe and secure. But if you change your career/education for this guy and give up everything.. you could have regrets about that too. Anywhere can you compromise? Maybe transfer schools or jobs? What does this guy think of you dropping your life to go wherever he is?

You didn't say what kinds of things "bug" you about the bf. Could you be nitpicking him just because he's not the other guy?

I agree with NuckingFutz, wait and don't rush into anything just because of all the feelings that resurfaced. Give it some time to think it through.