I dont have much time but did you ever think of calling cps or getting a lawyer for your grandson? Maybe they will make sure HE is safe and force your daughter to get help or to relinquish him to you or another safe person?
Our daughter eventually voluntarily.gave.her son to my other daughter so he is safe. It's legal now. He is doing much better.
I would not worry about your daughter, the adult. She.is able to do better than she.is and you can't help her or force her. You deserve peace. Your daughter is blackmailing you. She wants your money. So typical. That was all my daughter wanted. She gave up her own child when she realized that he would .no longer get her money from us. We closed The Bank of Dad and Mom.
This.ia very hard but.our abusive kids treat us worse than some abusive spouses do and we put.up with the abuse too long.
You may also try a shelter for domesric abuse. They will help you.. They offer therapy and other help. They know the system. Your grandson needs you to know the system.
We are done with our daughter but.it took ten horrible years. We are strong and close now and our grandson is safe.
. Please get help. Nar Anon is online now and helped us a ton. They do Zoom. Look up Nar Anon on the internet to learn when and how to get on a meeting
Love and prayers.