What you're going through is the normal part of this whole process of divorce, hurt, sorrow, pain and anger (which also manifests itself in less than appealing reflection on the former spouse and her new spouse). Add to that the pain and disruption it has caused your children and any normal parent would be incensed. Forgiveness does take time to acquire. I remember my first attempt at forgiving a man who hurt me deeply. The prayer was, Lord, bless the son of a (*&%$. Now that is not a very Catholic or Christian thing to pray, but God knew where i was at the time and He knew that was the best I could do. Please be kind to yourself. Working on forgiving her is not about her, it is about you, your peace, your children, your life and hopefully one day, your new wife.
That being said, let me offer a different possible perspective on the ex. You said that this guy looks like her father, and that in itself may be telling. If he is loaded, it is still about a father wound. A need to be taken care of on a level you (or any healthy man) may not have been able to or want to meet. And let me add that pointing it out to her is not a good idea.
As mentioned in these posts, it does take time to heal and reach a place of peace. For me it was prayer, love and support of friends and confession that helped me heal
God bless you in this season of New Beginnings.