Okay, so he is either wallowing in the guilt of his abandonment, or he is hiding something that he did while separated.

Which do you think it is?

Well, I know for sure he is guilty about the abandonement. The other one, not so sure of. No proof of anything other than I know he contacted an ex from college last summer. I know he also has friends on the internet. Claims they are all male (related to one of his interests). But he shows no interest in what I am doing or not doing. Seems odd considering the separation/affair. He thinks we need to be able to "do our own things, have our own interests". I agree we were too enmeshed before. Maybe we are going too far the other way now though.

Have you been in contact with the other man, or is there someone you currently have an interest in?

No and no
I assume the implication is that I will not be able to truly work on the M if I am holding on to some other person. I do see your point.
But what about just the idea of another person. Anyone can have those thoughts. Am I to go through life ignoring the fact that there are incredible people (men) out there who could be meeting my needs much better than H?
Can one person or should one person be meeting all my needs? This is where I get stuck.
My H has made mistakes, he has his own issues, but he is a good person and a likable person. But there are things that I will never be able to get from him. If I cannot get from my H the very things that I highly value in life (ec, love, passion) then are you saying I need to deprive myself of that the rest of my life? Because the trade off is lose my family (something I also highly value), get divorced. It does come down to that choice right? Black and white? No grey.