CD, I have read up on your stich and do feel that there is a good chance of DBing this quite successfully with the right game plan.

From my perspective, exposing the A or talking about the A to others is a cheeseless tunnel in your case. It may work for others. Disclaimer: My R was not saved nor DB successfully due to the fact that XW moved out of state. In my view, those who stay in the same house or town have better chances of DBing than those that move out of the state. With this disclaimer out of the way, here are some insights for you to mull over:

1) Stop focusing on the A and engaging in self-righteous talk about how W is doing you "wrong"
2) Focus on YOU and your interactions with W
3) Do get the Separation Agreement in place soon to protect yourself financially..no sense in harming yourself in this area
4) Let's face it: The OM is no catch! A 23-year old living with his sister and BIL in THEIR house!? Gee...I'd sign him up to wash MY golf balls and tip him in pennies
5) Your W is high on dopamine...the feel-good drug of choice...which makes her oblivious to the pain you are experiencing (yep...it sucks)
6) In a way, it is in your favor at this time that W is with OM since the longer she is with him or living with him, the flaws will begin to reveal themselves and her rose-colored glasses will crack and her dopamine will crack too! grin


So the plan of action is:

1) Positively NO R TALK unless W initiates it first
2) Look past the OM...not even acknowledging him (or even the A). I have done this several times and XW was discombulated several times
3) When interacting with the W, keep the exchanges brief and on the subject
4) Change things up a bit...like you CALL W and arrange for her to have D since you have PLANS (don't tell her what..even if you are going over to a friend's for dinner or drinks). The goal is to make W unsettled
5) Be the OM to the OM!!!! laugh

Follow on some good, basic ground rules:

1) Slap on the duct tape even if you are tempted to say something you may regret (that includes digs and/or snarky comments)
2) Do the 24-hour rule (even 48) if you feel the "itch" to act on something NOW or NEED to do something (those feelings are trainsitory and usually passes)
3) Ask yourself: Will this action/words bring me closer to the goal?

Dude...you are doing just fine! I'll keep you on my radar.