I hear you. . .but what's the downside to having a conversation first?
You've been having a lot of conversations, conversations in MC, conversations with her . . . where has it gotten you?
And let's say you do it your way--you have a conversation and she agrees to stay in the marriage, but then you spring on her the things you need and she will have none of it.
You need to show her real consequences. Tough love. She's not getting it any other way. Get and read a copy of James Dobson's "Love Must be Tough." Excellent book for someone who is being taken advantage of by a wayward.
You can't nice her back or reason her back into this marriage. She has to want it badly enough to endure some significant personal discomfort.
She's not there now. She may not be there ever. And let me tell you from personal experience that if they don't get there, you probably don't want them. If they don't work on their issues and determine why they chose an affair and fix what's broken inside of them, it is highly likely you will have another marital crisis. Maybe it won't be an affair, or maybe it will be a handful more affairs. But if she doesn't fix herself, you can't fix the relationship. Period. And if she's not owning the behavior, the deck is stacked against you right now.
You're convincing yourself that you were responsible for the condition of the marriage, global warming and world hunger all in one package. And yeah, you probably have some things to own in the marriage, but she has to own part of that "marital climate" also. She had numerous choices in how she dealt with it, as did you. She has to own 100% of the affair and 50% of the marital climate. So that is a minimum of 75% of the fixing that starts with her, assuming that the affair and the marital climate are equally weighted (which they may or may not be, depending on your situation).
Put it out there: if she chooses the marriage, she also chooses the work that it takes. No shirking, no excuses. The work starts with complete and verified NC with the OM. At this point, he does not need to be involved in any way, shape or form. He is legally a NON-ENTITY and remains a non-entity until he files a paternity action. She must be 100% on board with this--no filling him in on the pregnancy OR on the paternity test you are planning. There must be a huge consequence for this--I would say divorce papers and you file for 100% possession of the marital home and custody.
She needs to get into IC and start working on why she chose this course of action. At this point, MC may or may not be helpful. If it is, MC is also a must.
She needs to shed all "tools of the affair," which would mean any social media accounts, personal emails, change her cell phone number, etc. She has to be 100% open to you being able to see her cell phone, email, etc. A GPS on her car would also be a good idea. She needs to understand that earning back your trust starts in any number of very small ways, from producing the receipt that said she was at the East Side WalMart at 10:20 on a Saturday to you viewing her phone.
This isn't easy stuff, SAF. There is a reason why most marriages that are impacted by infidelity fail (it's about 2/3 or slightly greater). The deep dive into figuring out why the WS had the affair and fixing what is broken first inside them and then in the marriage is TOUGH.
That's why you have to be tough. It's okay to demand that this be fixed right. If it were a house exploded by a bomb or ravaged by a hurricane, would you want something substandard just nailed up? Would you want a few 2x4s and a tarp to call home? Or would you want to raze the site properly, carry off what couldn't be salvaged, salvage what you could and start building properly with a good foundation? If your home was damaged by water, you wouldn't just spackle over the damage, right? That would invite mold and rot. Same with a marriage.
If this is to be repaired, it must be repaired right. NO 2x4s and a tarp. No spackle. Tear it down, salvage what you can and build it back up right.
Own your shit, but right now, don't own it to her. You need her to step up, not use your assumption of issues as her crutch to not work hard.
Now do you see why a conversation isn't going to cut it? You need action. Concrete, verifiable and purposeful action. No more discussions. She's not listening.
Cat