Down and lonely after breakup?

Breaking up means that you believe the relationship is irreparably broken. And while you say you understand that and know that you do have to try and move on, the fact that you talk about a "plan" for getting back together that depends on her making a change that she wasn't willing to make to stay with you in the first place makes me think you need more time for that to really sink in before you start trying to establish a friendship with her. Just do try and stay busy and lean on your friends as much as you're comfortable with, and things will work out the way they're meant to.