2) Take your focus off of him and put it right on YOU. I lean toward this path. What is so attractive about a man that is cheating on you? Let his A go it's natural way. They typically burn out. MIL and immediate family know the truth, that should be enough.
"What is best for my kids is best for me" Amor Fati Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712