Have you thought about calling CPS, or having someone else call? When I was planning to divorce my N/BPDx husband, I told my lawyer about his alcohol abuse, and my concerns that he would drive drunk with our son in the car.
My L looked at me and said, "Call the police when he does that."
It never occurred to me to do that because it feels so odd to involve law enforcement (or in your case CPS) when it's our own loved one.
We have to make difficult moral choices when our loved ones are dangerous to themselves and to others.
The Family Law board has grandparents posting on it from time to time with these kinds of questions. You may find some help posting there:
https://bpdfamily.com/message_board/index.php?board=12.0