Ugh. I was just about to post that you shouldn't contact the OM when I saw this most recent post.
Nothing you can do about it now, but I think you should treat the OM himself as a non-entity. As others have said, any contact just elevates him in importance, and does not have the effect you want anyway. I don't even mention my W's OM by name. When he is referenced for any reason, its just "him", "this guy", "He", etc.
I think threats can/will be used against you, especially if there is an electronic trail. I'd say never do anything like that where a record of it could be saved.
I know it is a tremendous hit to pride and ego when there is another man in the picture, but I think you have to leave his eventual fate up to God. Rest assured, this guy will get what is coming to him. It is just not your job to do it. Read Romans 12; has some good info on this type of stuff.
Just for full disclosure if you didn't already know, I met with my W's OM shortly after the bomb (I had met him socially at a couple of prior events but we were not friends or anything), but kept it completely civil. I was trying to give him the benefit of the doubt, let him admit to a horrible mistake, and let him see the type of man he was dealing with - a class act and gentleman; not someone my W should be running from. It was my way of allowing myself to justify my view of him based on actions after that point. He apologized, but made no changes. It was to be my only contact with him, and I have never communicated with him in any form since then.
I gave him nothing to run to my wife about. I think you have to forget about the OM. Your issue is your wife. Don't let pride or ego dictate your actions. It's damn hard, but necessary, I think.
I don't think you should say anything designed to piss your wife off or put her on the defensive. Note that I say "designed to piss her off" not "that's going to piss her off"; as there are going to be some things that she's just not going to like, and that's that. But barking at her about her phone as she's walking out can't possibly help your case with her. If there is boundary violation deal with it matter of factly. State the violation, and the consequence, just as you would with your kids. I doubt you spank your kids anymore, right? Don't spank your wife; it won't work.
WAW Using God Me-43 W-40 M-14 S-11 S-9 D-7 EABomb 5/09 Separated 12/09