If his pressed charges this was no doubt yet another incident, in a long line of abuses against them and himself. Because of his addiction they've had enough.
His dad is probably hoping this may be his son's bottom.
Stay out of the way.
Due to your own circumstance, any attention from him must be a big distraction from the situation you find yourself in.
Maybe you can Find the strength to build your own life up and make it better for yourself and kids. Where does he fit in to this equation ?