I'm so sorry to see this news, I know how much it hurts. But, I can't say I'm surprised. To be honest, I expected it. And, you already knew -- that is why you were snooping to begin with. Trust me, if you think something is going on, odds are EXTREMELY high that you are right. That is, trust me, you should trust yourself.
Anyway, I wouldn't worry too much whether your W is in MLC. It doesn't matter WHY she is acting like she is. You can spin a thousand stories, and none of them will be right. Quit worrying about her. Quit trying to fix her. Quit trying to control her.
Now, what to do....
Leave the M. She isn't in it, you shouldn't be either. This DOES NOT MEAN having an A, kicking her out, etc... It means LETTING HER GO. You MUST let her go if she is to figure out what SHE WANTS FOR HERSELF. You can leave the door open for a renewed M, but QUIT HOLDING IT OPEN, and quit trying to get her through the door. Let her go, LET HER GO, let her go.
You need to find your own boundary here. If you are unwilling to live in a sham marriage (as I hope you are), then you need to take a stand and communicate this. I suggest you come up with your own plan about what you will do if things continue this way.
Call her on her BS -- it is hard for her to talk to you because SHE IS CHEATING, not because you are crying. She is annoyed with you and finding fault with you BECAUSE SHE IS CHEATING AND FEELS LIKE CRAP FOR HOW SHE IS TREATING YOU. The more she can find to pick on, the less bad she feels about herself.
Quit taking the crap.
Tell her directly that you will make your own decisions about separation and divorce. Tell her to get over herself, you choices are about what you need for a good life, not to punish her.
Validate her pain and confusion and tell her she is free to pursue her own happiness and that you will not judge her for doing so. If she chooses to sincerely try with you, it doesn't mean she can't change her mind in 6 months. It does mean, though, that she cannot continue to treat you with so little decency in the interim.
Quit being so nice to her -- tell her like it is. If she thinks that you will not be angry and hurt when she lies to you and cheats with OM, she is insane. A romantic R outside of your M is NOT ACCEPTABLE to you.
Your W is lying to you, betraying you. She is not being open and honest. She is not committed to restoring the M.
BTW, the most important thing to do is to quit giving her more of the same. That is driving her to continue to look for more elsewhere. I know it isn't a great time to bring it up, but the "accidental butt massage" = "accidental brush of the breast."
Quit pretending that your M is intact. It is not. Make new friends, go out, enjoy yourself. Do not base any of your decisions on what you think it will make her do or not do.
Your W is all over the place. Until you cut her loose, no real progress will be made. Until YOU MOVE ON AND LET GO, no real progress will be made. Again, this does not mean deciding on ending your M, but it does mean letting the M go for awhile. I'd suggest putting a time limit on this. Perhaps in one month revisit where you are and see if you are ready for separation or divorce. But, by all means, continue to let W know that you are not going to stay in an empty, non-monogomous M.
Stay mad for awhile. Quit being her H, she is not being your W. She is not treating you with decency or respect.
And yes, if she comes back again, expect even a few more incidents again after that until YOU really set a firm boundary and sincerely mean to enforce it.
Your W has a LOT to deal with and as long as it is easier for her to use OM to cope with things than to give him up, she will continue to do so.
You will be OK. You will be happy. You may find yourself in a good M with W or you may not.
Quit internalizing this setback -- it is HER cheating, HER lack of committment, HER lack of growth that is coloring her view of you. Don't accept her misperception.
Quit standing still for her criticism -- you are a wonderful father and HUSBAND who has stood by her, extended extreme compassion, stayed faithful, and tried your hardest to make things good for both of you.
Your pain and anger and confusion are justified.
Anyway, again, just LET HER GO, LET THE M GO... Quit trying to figure her out. Really. STOP. Do not obsess over MLC. Do not worry about what kind of strange power OM has over her. Do not worry about her disfunctional family of origin. What matters is that she is not in the M. It does not matter why.
By all means, DO NOT tell her what she wants or needs. Stick with what YOU want and what YOU need. You can ASK her what she wants and needs, but don't project your wants and needs, what you think is right, onto her. SHE DISAGREES.
Just live well for yourself for awhile. Make clear to her that an uncommitted M with you is not in the cards. Tell her that you will not remain more committed to the M than she is. Figure out what you want.
Major hugs, Oldtimer
(Oldtimer, Oldtimer's H, and Newtimer all doing splendidly.)