Pete, I've just read through this whole post.
Brother, I'm so so very sorry for what is happening. I was there myself 7 months ago.
It was just an emotional affair, phone calls. At least that's how I found out. It was NEVER physical.
Finding out she had fallen in love was a wrecking ball to my gut but at LEAST it wasn't physical. Heck he lived in a different state.
Then I found out they were STILL communicating, just using snapchat and whatsapp, hidden on her phone.
That's when I moved out for 30 days - it was going to be a 7 month lease but she begged me not to do that. (In retrospect, this was one thing I did that actually made me feel immensely better, probably because I gave agency and power back to myself.)
During that next month I found out:
well we did send photos and messages to each other, but they were never inappropriate.
yes we did have sex over facetime but only once.
Then two months of thinking I knew everything only to find an email with a letter from the AP about how he knew she wanted him to leave his wife and be with him but he just couldn't do it because he had kids.
And then the ACTUAL truth:
they had been physical, multiple times, and he has lots of videos of her he took while they were together, that he liked to 'enjoy' when his wife wasn't around.
No matter how you think you'll act if you find that out, it doesn't matter. It's going to destroy you to your soul. You can't prepare for it.
I can type this now without spiraling out of control, but there's a 0% chance that would have been the case two months ago.
Should I have left her and gotten a divorce? People on here and elsewhere will give you all their advice but none of it really matters because they're not YOU.
This is not to say that most of what people have been posting on here is valid, because it certainly is. Take care of yourself, your wife may or may not be ready to give up what she's got, face the truth and shame of what she's done, or quite frankly she may not even care what you do if she's fallen in love or limerence or whatever with the AP. There is NOTHING you can do about her but you CAN take care of yourself.
Even after all the gut wrenching nonsense she's put me through, I'm doing everything I can from my side to make it work. Including focusing more on my relationship with God and praying nonstop for the strongholds and attachment(s) to be removed.
It's going to get much much worse before it gets better. Work on your communication skills and try and read some books (Not Just Friends is a great one) to help you understand what's going on in their brains and how to avoid similar situations in the future. If your communication skills were not great before the incident, you 100% need to work on them now because there are going to be a lot of conversations you'll need to have.
Sorry you're here.