Originally Posted by morituri
Inform the OM's wife, get tested for STDs and file for divorce. Your wife is addicted to the OM and after promising you to have no contact with him, she turned around and did it again, this is a second betrayal. If she truly loved you she would have walked through glass to restore your trust in her after promising to end all contact with the OM. You need to man up and let her see that there are consequences to her actions.
I would do this.
You don't have to finalize the D unless you want to but doing this will make her come down from the A and make her panic from losing you.
You can't be nice to her or "understanding", you have to put your foot down and tell her its over then let her try to win you back. As long as she has any feelings at all for the OM there's a chance she will relapse back into the A (technically it sounds like she never ended it).
If you don't play hardball, you will fail.