T.,
Welcome to mamapedia!! How nice of you to want to help your friend! It's tough in an abusive situation as you never know if the abuser will turn on you.
Take your friend to a woman's shelter. TODAY. Do not allow her to stay in that home another night. Let her know that if she stays, she may not walk out that door ever again. Does she want to do that to her children? This "man" (using word lightly as a real man doesn't need to hit or belittle his wife to make himself a "bigger" person).
Remind her she's not doing this JUST for herself, but for her children. Her children DESERVE a life with a WHOLE mom...not a battered and abused mom...THEY deserve a life without fear.
IF you talk to this "man"? It WILL make things worse. He may believe that you are having an affair with her and that's what caused her to divorce him. She was strong enough to file divorce papers...now she needs to be strong enough to fight for her kids....
I wish her much luck. She'll need it. Let her know she's NOT alone. Let her know she's doing the right thing. Let her know that IF he puts her in the hospital with her beatings? He might take it out on the kids, if she's not there to protect them...