Marina, I am not sure I am following but your kids do not need W right now. She is not stable nor sane and she is abusive. I don't understand why you are even considering her having custody. They can see her often but you should be their guardian and make decisions for them. She is not a fit parent right now, based on what you have written. I feel the same about my H. He is not able to parent my kids. They need stability and peace, not to see someone just because she used to care for them. I would be more patient, let things happen, if W comes out of this even a little, you can always change the amount of visitation. Don't give up on your kids. Based on what you said, it seems unsafe for them to be with W.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.