Thank you for your very compelling question. I see you are hurt by this relationship, though I really can not tell how much.
The answer is highly subjective. It really depends on how one approaches relationships,and where your values are.
From my perspective just listening to the story, I am immediately impressed with how not ready he is for any relationship, and how immature he appears to be.
I am also impressed with this idea of staying in relationship or carrying on a relationship from the perspective that...someone owes someone the relationship.
so I need to ask this question as part of the answer: Why would anyone want to fight for a person to be in relationship with them, out of as since of debt, or who is obviously not into you. This perspective is called scarcity. That is a person (this includes you and him) comes to the relationship unfulfilled in some way. You need or want to be together to get something from the other you do not have. This is particularly why he is in relationship with the other woman, and now owes it to her, but expresses a need to be with you as well. this scarcity is also why you feel, at some degree, that you need to have him in relationship with you, and express a desire to fight for him.
YOu appear to be more mature and complete than he is, and this makes you more ready. But he is not.
Other therapists and relationship experts,and degreed persons may describe this differently, but it comes down to the same thing. Trying to find in each other, something you do to have for yourself.
Laura, here is my main point: why would you fight for this relationship, or for this man, if he is not already whole and complete; if you and him to together do not make a greater whole; and if he wanted to be with you, he would not be with her under any circumstances; but he would be vested in being with you, which he is not right now.
I thought your original plan was good. Please do not contact you. but, since you have expressed a desire in your question to perhaps give him another try, a stance that keeps the lines of communications open, but that avoids contact until he is ready, may be a better approach.
IN my opinion, you should be looking for someone who is whole and complete
Someone who does not need you, but wants you.
Someone who is available.
He is clearly not available at this time.
I would look elsewhere, and if he is available and matured, perhaps a year or more later, and you are not already "taken", then you might consider it again. You can keep the lines of communication open.
come to your relationships, not from a perspective of scarcity, but from a perspective of plenty. that is, you are whole and complete, and you are looking for someone who is at the same level as you. It could be him a year from now, or it could be someone else.