I should have stuck to my initial response upon finding out, which was to tell W she was more than welcome to take her butt out the door, but the kids were to stay with me. I would NOT have been the nice guy and volunteered to move out instead. In fact, my first thought was to take all her belongings (and MIL's belongings) that first night I found out (while she was out of town) and throw them out in the yard. I then should have changed the locks on all the doors.
But of course my actual course of action was couched in shock and confusion from the bombshell, and I still had hopes that my spouse still had a heart and that we might have been able to work things out. It took me too long to "catch up" to the fact she was long gone already. I should have taken a 100% tough love approach and dried up the tears and pleading immediately. I should have realized from the start that the "marriage counseling" she initially agreed to was just a ploy to buy more time and buy cover.
I should have immediately exposed her treachery to all of her family. I should have sought out legal counsel sooner. I should have never taken a management position right before this bomb fell.