Between a keylogger and the other things you do have access to, Amy, my suggestion would be to -- in this order:
1. Gather more intel
2. Expose to CLOSE family/friends -- ones you know will be supportive of your marriage. Tell them that W is likely going to lie to them about this, but that you wouldn't be coming to them if you didn't have iron-clad PROOF.
3. Confront wife. Tell her "I know all about you and ______, and it needs to stop, now. It's incredibly disrespectful to our marriage, and I won't LIVE in an open marriage."
The reason you do these in this sequence is that it strengthens your hand to pre-warn friends and family that wife will lie to them, but that you will NEVER lie to them. Then, when she does lie to them, you gain credibility (hat-tip to Allen A for this one).
You seem afraid to do all of this, and I COMPLETELY understand. But it doesn't change the fact that it's what NEEDS to be done. Will she be livid? Absolutely.
