I know snooping is against Sandi's rules, but at least for my situation, it led to me standing up for myself. I was content with GALing and being positive around W while I assumed she was not in contact with OM and was trying to figure things out. How it will contribute to the end of my situation, I don't know, but finding evidence finally gave me the courage to put my foot down, be a man and establish a boundary similar to you.
I guess what I'm getting at is it's not about whether you snooped or not, but how you handle what you've discovered. I know how it can eat at you, but you've got to resist using it as ammo in discussions you have. Easier said than done.
Zew, I'm right there with you on your 'you don't know how you'll react until you've lived it' comment.