Welcome to the forum, I'm sorry that you find yourself here but you are in the right place.
I'm not a vet here (please listen to them, they know what they're talking about) and I've only been here around a month or so myself. My M is not in a good place, so temper any advice I give in the knowledge that I'm posting to you because I feel your pain brother, not that I know of any magic wand that makes it stop.
I see a lot of similarities between our sitch's. I've also been married for 20+ years, we're slightly younger but we've been together all our adult lives too. I also have 4 children, some of similar ages. I don't have a known OM in my sitch at the moment but it's only a matter of time until I'm where you are now unless we R. That doesn't seem likely at this stage.
I know exactly what you mean when you say that you don't even know how to detach. I have had the same thing, but it is crucial to your health that you try to work on yourself (for you) right now. I know it's hard but you have to try not to think of your W with the OM, it serves no purpose and the mind is a powerful thing. Don't let it be messed with.
I agree with the other posters above about protecting your children, even if you don't want to be the one to have to call the cops and say she's drink driving. The "who" does it is less important than the fact that it's done. Maybe before you get to that stage, you should raise your concerns with her about it, and the fact that she is exposing the kids to the OM. I wouldn't want that either. She will be defensive about it all etc, but you should probably try to talk with her first.
Every post above has some real wisdom in it, and all have the best advice you need right now. Please try to follow as much of it as you can. I'm doing the same in my sitch. My W and I have been NC for 6 weeks today (she left a few days before Xmas), apart from the odd text about finances/kids but all short. I've been struggling to apply some of the DB techniques I should because I, like you, struggle to accept that my M is over. Sorry to be brutal, but your M IS over, at least in it's current form.
Our W's appear to be going through a similar thing in that they have always been a W and mother and never really had a "single life" (neither did we as H's) - they don't know who they are etc. As I say, I've heard the exact same things. There's no turning the clock back for anyone, and unfortunatly, your W (and mine) need to walk the path they have chosen. I'm sure that in time, they will see that the grass isn't always greener..
My thoughts are with you and I'll keep up with your sitch. Hop over to my thread for a read if you want ("This can't be the end!" in Newcomers), you may see some similarities and/or advice that I've recieved that can help you too.
The people here have been great, and I don't think I would be coping so well without being here.
Keep posting.
Barry.
Me 40 W 38 T 23 M 21 S21 S19 D16 S14 BD 19/12/2014 D mentioned 27/2/2015. I filed 08/04/2015, D Absolute 04/11/2015