The most recent post caught my eye and I went back to read all of your threads to get caught up on your sitch. You are in a very precarious position right now that has the makings of a potential reconciliation.
I liked how you handled W's inquiry about moving in. Good job. Here is what I suggest as the next step:
Keep your head stewed on really tight and be the cool Clint Eastwood.
In so many words, you can tell W that trust is broken and that you are not comfortable with the notion of her moving back home. Then lay out the conditions as the following: 1) continue with MC 2) absolutely and positively not willing to live in an open marriage for its not what you signed up for 3) for W to stay at her place for the time being 4) you are feeling uncertain and wary given the damage and hurt she's inflicted on you and son with her choices
Then say this is all you are going to say to her at this time because you do not yet fully trust her enough to open up to her. Then sit tight and observe going forward.
The most important thing you can do that will ensure a successful reconciliation is not allowing W to move back home just yet. She needs to get her chit together FIRST before you would ever consider it.
Keep your wits about you and you'll be just fine. You're doing a bang on job with not initiating anything or bombing her with photos and nonsensical stuff. You're on the right track here, buddy.
