Forgot to mention, Coco, it's likely that your son will need counseling, no matter what happens with your M.
What your W is doing to him is robbing him of the innocence to emotionally be a child. He's her caretaker. He's her partner. And he is in no way capable to handle these things.
If he doesn't get help for it, he'll grow up and find another woman to caretake, and the likelihood that a woman who will be looking for a man to caretake her emotions is not a healthy person is 100%.