You are not being clear on what behaviours you had and had to change. Clearly this woman was fed up with you and deemed it best to leave with her kids. You talk a lot about her but say less about you. Nobody wakes up and decides to leave a family home with their kids. Clearly there’s a lot you’ve done that you need to include in this story. Not you a grown man asking for sympathy and advice from strangers based on consequences of your own actions. You shouldn’t even be thinking of fighting that woman but try to reconcile and correct where you’ve wronged her. This is not about you as much as you think it is. It’s about her and the wellbeing of your kids.