whatever you're doing for her needs to stop. She'll whine and say you're being hard on her and boohoo per WW. Oh well. You're are enabling her in the affair by still supporting her.
If your S asks where mom is, tell him to ask her. Don't cook for her. Don't support her. She doesn't want you, so you aren't going to try for her. If marriage is so easily set aside in her mind, then OK that's it. We're done, I'm not here for you anymore.
When you say stuff like you're "going dark" it just shows that you aren't committed yet to pulling the plug. If I can see it, she can see it. The longer you play Plan B, the worse she will treat you.
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.