none of us are perfect, and we all learn along the way. Hindight vision is 20/20, we also know that.
You are harboring guilt and remorse about something that you cannot change. The best you can do is realize that you are happy now and your exW has found her happy. Yes, it hurts to have to split time with the kids. You may have feelings of guilt and remorse, but you can't carry that for her not being willing to do what it takes to heal the marriage. It's not yours ot own at all.
So what "what-if" are you holding onto? Is it a what-if you had control over? or is it a what-if that would have come about something your wife only had control over?
I lived with a lot of what-if's too. I knew my ex was a bastard. (pardon my language, but he is). I knew it when I married him, but I was in such a crappy place in my life, anything that appeared to be love I was holding on to. Then I willingly had a child with said bastard. She is the best thing in the world to ever happen to me, but I harbor a lot of guilt knowing I chose this man as my daughter's father.
But there I can't go back in time. So I just march on and learn for the future. You seem to be doing the same. You will let go of it in time, I am pretty sure of that.