My usual strategy is to suggest you expose his infidelity to close friends and family who may pressure him to end his affair and act to respect you again...
Failing that, I would suggest cutting him off from "emotional support" entirely.. he's not living with you so simply NOT CONTACTING him at all is do-able... no access to home, you, or family etc...
If he cheats and you introduce no consequences, the affair will run longer. The sooner you attack the affair head on like this the easier it will be to end. The longer he's connected with her the tougher the fight will be to get him to walk away from her.
