Just read through this and glad you nipped the temptation to continue flirting with this other guy in the bud as quickly as you did. Can totally understand how knowing the history with your H it was flattering to have this other guy showing such an interest.
I personally don't see the point of telling the OM's wife for the simple reason you don't reciprocate the feelings OM has had and you told him it was inappropriate. She may not believe you anyway and it could just cause trouble between you and your H at a time when you are reconnecting really well.
I would be careful and print any email and replies you send asking him to quit bothering you. Try ignoring him completely for a week or two and make sure you're never alone if he turns up. After all he KNOWS your H is away and may just arrive on your doorstep do not let him in under any circumstances.
Maybe I'm just one of those people who can see danger where there isn't any but I would be very careful for a while of this man.
Anyway on the bright side glad things are going so well for you with your H and hope you've bought lots of nice undies for your trip next month. You'll make everyone else jealous of your fun.
