The ideal situation is having the OW's husband tell your husband something like :
"I would like to save my marriage. I love my wife, despite the damage that you have done. She's my wife and I am going to fight for her. Please stay away from my wife, my children, and my home."
THAT is a message all affair partners need to hear... that they are destroying/attacking a family unit, kicking a nest out of the tree so to speak.
YOu will need to support the OWH if he's willing to try... he may need a forum like this.. MOST people don't understand troubled homes or how to manage them safely... they listen to mood rather than commitment, they give up and lose patience, give people bad advice etc.
There's a film called "The Break Up" with Vince Vaughn and Jen Anniston. In that the couple have a huge fight and isolate from each other while still living in the same home. They go to friends for advice and get REALLY BAD ADVICE that makes things WORSE rather than better. THAT couple end up breaking up because they went to the WRONG people for support... its ag ood example of what NOT to do when things are difficult athome.