Transparency (and no-contact) is something you ask for when SHE is ready to return to the marriage, and tells you "I'll do whatever it takes," or asks you "What will it take?" You're nowhere near that point yet.
Don't use exposure to OM's wife as a weapon. Either do it or don't (and I generally believe you should -- why should she be the only one of the four of you that doesn't know the truth about what's going on?).
I'm with Coach -- don't do anything for 24 or even 48 or 72 hours. If she asks you "what are you going to do?" (and SHE WILL!), just say "I'm not sure." She deserves no answers right now, and you're not prepared to give any.
If you'd like to discuss what you found, you can find me on Facebook. Just look for the guy who sang "Feel Like Makin' Love" for Bad Company (but without the "d"), and lives by the Jaguars.
