Be really careful about letting your 12yo be the conduit of information about what your W is doing and how you feel about her actions. Don't put him in that place, and don't let him be there if he's using complaints about mom as an easy conversation topic to have with dad. Your care and concern in response to his comments will encourage him to report more and get more of that positive attention. It's just my opinion but I think if he's feeling down about lack of attention from his mom, focus on teaching him some ways to address that directly with her such as to ask her to make a plan to play a game with him or do an activity with him. He's going to need to learn how to navigate the relationship with his mom and get his needs met, and he's old enough to start learning how to do that. I would discourage him from reporting her dating activities to you, and if he complains to you about it perhaps tell him it is completely normal for divorced parents to date. You may telegraph your disapproval to him so he sees this topic as a way of bonding. There is usually stuff going on under the surface with kids of this age that neither of you may realize is happening if you're not on the lookout for it, and dad=good mom=notsogood is not really healthy for him. He's got to learn how to make the best of his reality.
You personally sound like you're in a pretty good place; it's been a long journey, huh?
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.