I agree, I don't think I will ever forgive my XW for what she did to ruin our family however I am to a point to where I don't let it consume me.
My revenge comes in my own happiness. My successes and moving on with my life.
I am civil with my XW, I can be in the same room with her, attend our kids functions together, have a joint birthday party as well but that still doesn't mean that I forgive her. I just put my kids first and what is in the best interest of them.
As far as her BF goes. He was not around when my XW first moved out. She did not meet him until several months later. While we were technically still married she was actively dating and started dating him before we were divorced. It is a reflection on the both of them and their characters but when she has our girls 50% of the time there is not much I can do to control their interactions. As long as he is kind to them and a positive influence what can I do when they are in her custody? I have to trust that my XW would not bring someone into their lives that shouldn't be there. My girls have never made a negative comment to me one time about him either. My oldest is 10, she is old enough to articulate herself.
They have been dating for over 2 years now and he has never come to 1 birthday, 1 game or any place where I am going to be. I have never met him but it's not because I have thrown down the gauntlet. In fact, I told my XW that she could bring him, that it didn't bother me. He still hasn't shown up. So who knows.