Meggie...I think you have come to a place where you cannot stand him yes. However, I think you are worried about what will happen to him if you leave. I understand to a point, but I am really scared he is going to hurt you.
I just think his parents are basically saying they are not going to save him this time. If you leave, would he pay the mortgage at all? You may want to call the mortgage company and tell them what is going on and see if they can freeze it or defer a few payments. My friend did that. They so badly did not want the property to foreclose that they froze her payments for 12 full months to let them figure it out. She had Wells Fargo.
So I guess the financial part I understand. However, I do not understand what you want his parents to do. They cannot make him stop anymore than you can. I think if you call them you should say you know he is not going to change, they know he is not going to change. Put the focus on the grandchildren.
Keep checking on things from the attorney. Don't engage with any of his quackery. You can do this, we are behind you 100% my friend!