She wants to hurt you, because she is hurting. I am sure she does not always hate you. I am sure she loves you at times, and then a mood takes over and she remembers all these things you did to her to hurt her. And then she becomes enraged. She feels justified. She is interpreting your actions as being ways to hurt her. I am sure she is suspicious, especially because of your legal background. Like you, She also feels the need to protect herself legally.
She has been feeling hurt by you for a long time, and now because she detached first she can hurt you. She is angry and she is simply acting on her emotions.
I am the LBS, but I feel similarly torwards husband (I keep my feelings to myself though, but I long for the day to make him understand what I am going through). The mistrust and legal implications play huge roles. It is really sad and I am sorry for your situation. For me personally, the lack of communication from husband makes me more mistrustful and more filled with rage. It makes me detach but in a bad way. When he interacts with me and discusses feelings (without anger or argument) and really understands what I am going through I feel more connected. His phony validation texts annoy me. Obviously you cannot initiate this because you are the LBS. I am only mentioning it because I think it's a universal male -female struggle.
I wish I knew the best answers for you. It is so difficult when there is so much at stake. Even more difficult in your case as a step father that really wants to do the right thing.
Can you believe that my kids biological father is fine with less then 30% of the time with them? When I was sick and needed extra help he was too busy to help. He took off all these vacation days in summer and not once helped my parents with kids while I was working. In a way I am lucky because, legally I won't have to worry too much regarding custody. Although he makes little comments that say if I ask for more money he will ask for more time with kids. This is why your story stands out to me so much. Because you are truly a good man to be so concerned with making sure these children have a positive male role model in their life. Don't forget what a good man you are.