Let them communicate via email or maybe a third party. There are ways and if he wants it bad enough he will do it.
I only say what are you going to do different as I have been down this road with my now exh. He knew I would come back over and over with a bit of convincing. Now he knows I am dead serious and his life is sprialing out of control.
Lay out your demands and let him jump to them.
Me: 46 FWS: 36 Married and Divorced 4/07, Pregnant 7/07,False R 7/07 Baby Girl born 3/08 Kicked him out because OW: 7/08 5/10 He realized what he had and lost. Moved home! REMARRIED 3/14/11!!