Thank you all for your support and replies. I want to clarify a few things.
I did immediately get tested for STD's. That was an awakening to the reality of the situation.
I have thoroughly consulted with an attorney, and know all of my legal rights, including suing for damages pursuant to the affair. I am in a no fault state, short of damages, the A does not influence the D situation in my favor. I come out ahead in a D situation no matter what happens, and she also knows this, she had consulted with her attorney long before even the separation, I found out much later. This may be the biggest factor in her decision for R.
I have a great IC, and that has been indispensible.
As for my friend, and our R, here is where it gets complicated. Initially I had put a NC ultimatum on him with both myself and WS, and I would have sent recordings to both his ex's, his mother, his daughter, everyone in his life deserves to know what kind of person he is. I also have much more extreme ways of punishing him, and I feel no need for physical recourse, physical pain is a trivial thing compared to what I have experienced.
After several weeks, I reached out to him because there were some details I had not been able to get from WS. He exhibits all of the emotional contrition that my WS lacks. Our R is strained to no end, and it is very one sided (on his part). He reaches out to me now every time my WS contacts him, with full details - I can corroborate the validity of this, because I also have ways of knowing from my WS side, and they do not know that I have this knowledge. So that appears to be authentic. But they are both capable of such incredible depths of deception, I second guess everything.
He knows how bad he fucked up, and is devestated. It is unforgivable, but our inroads have made the illictness and practicality of the A impossible for her. That certainly could have been a factor for me in the first place.
To her credit, most of the times she has reached out to him have been for my benefit, regarding concern she has for me, but they also are likely lightly veiled pings for more. He has shut her down completely at this point, and they have finally blocked all their phone numbers and social media now to preserve the NC requests. I will not tolerate that any more.
I have operated under a bubble of ignorance for a long time, but no more. I can be a formidably vindictive human, and am quite capable of ruining both BF and WS lives, emotionally, financially, and more. I am choosing the R for both of these situations, not out of weakness or desperation, but deep pity and empathy for both WS and BF, and a desire to preserve our children's chance at the best life they deserve.
All that posturing and preparedness aside, I still can't change the emotional reality of this situation. I can't imagine ever trusting anyone again. The rollercoaster is vicious. Every time I feel like I am doing the right thing, I get punished for my vulnerability. Madness.