Re: daughter.in.Law, Son won't see
Using physical violence will do nothing but get "you" in trouble, give your daughter in law more ammunition and probably turn your son against you.
Until he decides to make a change in this situation there it nothing that you can do, you'd be smart to stay out of it and let him deal with it. You can't make a decision for someone else, they have to do that themselves.
I know it hurts to have to sit back and watch this....but honestly you don't have much choice.
You might concentrate on the kids, making sure they have support....it sounds like they're going to need it growing up with that mom.