Dingo, I'm sorry you find yourself here, but it sounds like it's a better fit for you than the last site.
Have you read DR yet? That's generally the starting point for everyone.
I was reading "Surviving an Affair" this morning, and it really hit home for me. After reading your sitch, I see a lot of similarities as well. Your W's response to you snooping and finding the invite? Typical. It's discussed in the book, and my own W did it quite a few times. It's a way to project guilt on you (which looks like it worked) so that you stop questioning her and she can continue doing what she wants. I'd guess there's a 95% chance her A is continuing.
So here's the tough part. Affairs typically die a natural death, but it generally takes a change in the situation for that to happen. As long as she's got both of you, things are probably not going to get better. I'm not saying do anything about it yet, but think about it.
In the meantime, get to reading, start thinking about things you want to change about yourself, things that you don't like, things that your W has complained about. Think about how you want to improve yourself as a person. That's a lot of work, and it will drain you....so balance this by GAL. Get out, meet people, do things you've always wanted to, exercise, etc.
With regards to your setting a boundary of her not seeing OM outside of professionally, how are you going to enforce that boundary? Has your W agreed to it? Generally, boundaries are for you....to protect you. They aren't meant to control other people.
