This is like a movie! The retired detective and his WW booby trapping her journal and sweeping for bugs. I'm sorry, I know I shouldn't find this entertaining but I can't help but imagining you guys trying to one-up each other on this. Maybe she was never really an MC but is actually a deep undercover government agent who has been lying to you all along! Her counseling work is just a cover! And maybe the OM is a sting operation and once she gets the OM to confess to treason she'll fall back into your arms and say it was all a ruse to save the world and you'll tell her you knew it all along.
Anyhoo... Glad to hear the L told you to stop snooping and sincerely hope you do. And, agree with the others on the damaging side of all of this. Yes, she's a weak and selfish person who is blowing up your lives for weak and selfish reasons. Good riddance. Why on earth would you take a vacation with the kids to a place you know she's been with OM? Go somewhere totally new and make new memories with your kids. Trying to F with her head by vacationing there and going into the garage (though I don't quite understand what happens in there... do you have it bugged or something?) is just another form of attempted control. Trying to make her feel guilty or freaked out or realize what she's doing... that is all about her.
Of course easier said than done, but I just want to add my voice to the others about trying to stop this behavior and refocus your energies on yourself and your children. Put yourself in your own shoes ten years from now and imagine explaining your behavior to a mutual friend... do you really want to say that you tried to ruin her career and sent a file of damaging evidence to the OM's LBW? I kind of doubt it.
Hang in there. This is all incredibly difficult. I have faith you can rise above the feelings that are driving you to engage in these unhealthy behaviors.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing