You continue to sound like you are doing well, Elmo. Keep your eyes forward and keep moving onward.
It is great that you have a DB coach as that is the best support you can have, next to Michelle. Stay with your coach's recommendations.
You mentioned a few things I'll take in order of precedence. Your W entered the swipe code in full view. You snooped and found no evidence of OM. Your W was in a good mood on a Friday a couple weeks back and not so much on the Sunday following.
First... STOP SNOOPING!
Second, her mood that Sunday could have been for any reason, but... her mood on that Friday could have been because she was excited to see the OM that weekend, and then something negative happened between them at which point, by Sunday they had "split up" and in order to prove that to you, even as an unconscious act, she did not hide her swipe code from you...
OR... I could be completely wrong... Meaning, her emotions have reasons that you may or may not guess correctly. And it happens as often as not, you will be wrong. Just because you don't see any trace of the OM doesn't mean he isn't still in the picture.
So in the end, stop snooping and stop trying to involve yourself in something you cannot control. Keep working on yourself, become a man that only a fool would leave, and hopefully that will save your M, when it will at least save you from a negative future.
As mentioned, listen to your coach. GAL is important and you may want to try some 180s. Either run these things by your coach or do them. You DO have this board and the DR book to look into to give you ideas of what you might try. Just do everything with good intention and all will be fine.