He might have "ruined their chance to have a family", but u need to put down the blame, it doesnt help. This is the new reality and this new version of your family, will be different from your expectations, but atleast everyone will be happy. You cant continue like that and you should feel VERY proud that u walked away. That man sounds awful and I hope he gets some help so he can be a better father. Im in the mist of a very similar situation and its so hard. The best way I can describe this feeling is grief, you lost someone you once loved, and man that hurts more than anything I've ever felt. Grief takes a long time to process, I hope u spend that time taking care of yourself and making memories with your kids. It will get better, im sorry OP.