I would make sure the OWH knows asap too... Your H's likely planning damage control.
Tell the OWH where your H works too.. and make sure your H KNOWS that the OWH knows his work address...
He's been messing with people's lives for a while now because HE had more info and let others out of the loop.
Turn the tables on him and make sure he KNOWS the tables are now turned around.. the more he sweats the quicker he wakes up.
This will VERY likley start a FIGHT with your H and the OW... when you bring reality down on those two infidels they FIGHT.. the more fights you cause between them the better.
More reality = more conflict for those two.. and more fighting.. they will hate each other in no time... just keep a distance and keep hitting them with reality from a distance.
Keep a lot of intel handy. ALWAYS be civil, but don't tell him anything. don't cater to his whims or complaints.
Keep distant but don't be mean or name call... hold your ground but be an adult... think of him as a five year old who's gearing up for a HUGE tantrum.... just be a mother instead of falling to his level, don't let him bait you... be the adult.. a DISTANT CIVIL adult. But share no info unless it will do damage on his end.. you don't want him hating you.. if YOU don't do any name calling his OW will look bad... out mature this OW, its easy.