I agree with the others here. Take 48 hours to cool off and think. Could this have been a chance meeting? I don't think H would have purposely met OW with D along. I know I wouldn't put my kids in a position where they had to lie for me.
I know H meeds to become transparent, needs to let you see every thing he does. Remember OP in an A is like an addiction. Will H go to MC? That would be a good place to discuss the boundaries you need to set for H, what he needs to do to prove to you it's over.
Mike
M 51 W 49 S26 S25 D24 D19 Married 27 yrs T over 30 S 7/12 D-bomb 9/26