I haven't read through your whole thread yet, so for give me if you have already done this...but if your W doesn't tell your so-called "best friend's" wife about what they've been doing...so that you can verify it, YOU ought to do it.
His wife has the same right to know what's going on as you do. You of all people know how it feels to find out what your spouse has been doing...and knowing that, you need to ensure that she is informed of what her husband is doing, so she can make her own informed decisions to how to proceed within her marriage and with HER life. Your W may not be the first...or only woman he's done this with, and his wife has the right to make the same informed decisions you do.
So, if your W does not tell her what they've been doing, in a manner that you can confirm (such as a phone call in front of you)...then YOU ought to tell her, and tell her how you found out. There are a couple of reasons for doing this...it totally exposes their EA, which is one of the best ways to ensure it ENDS...even though your W and your "friend" probably won't be big fans for yours for telling his wife (they should have thought about the consequences before they did what they did.) It also ensures that YOU don't harbor their secret, harboring their secret is not helpful to the situation, it is akin to aiding and abetting the infidelity in their marriage and it makes it easier for them to simply go further underground with their EA and hide it better.
