I should note that my wife is already looking for another job close to where the OM lives (about 2 hrs away) and she sid she wants to find an apartment near there (but I suspect she migh just try and move in with the the OM in his apartment).
Cut WW off from you financially. Do not finance her A. Get a another bank account and deposit your paycheck there. Take at least half the money in the existing account and put it in your new one. Since POSOM does drugs the last thing you want is for WW to be giving him money. If WW doesn't know about the drug use he can still ask her to "borrow" money because his mean BW is greedy and not giving him any money.

I'd expose to everyone as well as tell them about OM's drug use and all his other charming personality traits.
It's too soon to know what you want. You'll want a recovered M in the morning and want to kick WW to the curb by lunch. No hurry to decide if you want to file D but you need to protect yourself financially. If she moves abruptly will you have to move out of your current apartment?
Did OM's BW say anything about OM leaving their home?
My wife said she will continue to pay half the mortgage payment when she moves out. So no worries there. But that doesn't help me with the other bills - electric, phone, maintenance, etc. So I won't have to move, but taking care of the house by myself, plus two large dogs will start to affect me at some point. Financially I'm not too concerned as we both have good jobs. we have one joint account, plus separate ones. I might try to divy up the joint account and close it, along with joint credit cards.
The OMs wife has already moved out of their apartment (did so in mid-February) and in with her sister. The OM wife's has financially split away from him. I may have already said it, but she mentioned her husband is broke at this point. They live a large expensive city so the rent must be a killer. Plus he just has bad spending habits as you can imagine.
I guess I'm hearing some people say to move on and be done with her, plus some people say to try the Plan A/exposure/Plan B route. I'm just not sure if I can make a decision on it right now. Lots to think about. My problem is I"m such a laid back guy that I'm allowing her to walk all over me. I can't legally kick her out (plus hopefully she will move out sooner than later), and it would kill me financially to move out myself. And I hate getting lawyers involved, because I rarely hear of cases where people came out with a net gain after paying all the rediculous fees. I guess I have some time to see what happens. I'll be talking with my MIL this week. She talked to my wife face-to-face yesterday about this mess and I'm interested to hear what she thinks now.