Some will say the timing is important...the way I see it here is you are thinking you've made some progress and don't want to rock the boat.
She is cheating on you- what do you think she'll be doing until Sunday?!
I would contact OMW whie the iron is hot- you mentioned earlier being fearful of ruining another M----he is ruining his own M. Think about his W sitting there buyig his BS...you have the key to bring her to reality as well.
I outed OM1 to his GF--she loves me now, thanks me everyday for letting her know...and the good news is OM1 is out of the picture completelt- the bad news is W is now w/ OM2...who is single and did not choose his GF over my W.
Am I better off? Not at all, but I helped someone else and did what was right.