This is how to treat a cheating husband: 1- You should treat him very kindly. 2- You should advise him and admonish him. 3- Don’t let many people know about what your husband is doing. 4- Fill his time with useful and beneficial things. 5- Offer a lot of du`a for him to be guided.

It is permissible to engage in coitus interruptus and to use a condom if the wife gives her permission for that. For more, see the detailed answer.