Sounds to me like pretty solid proof she is actively engaging in an affair. So where you go from here is up to you. I would suggest assuming the worst and basing your actions on that. Even if you want to save the M you still need to treat her like a WW because that's what she is. Go dark. Also quit snooping, she's having an A, you know she is, so there's no point in snooping further.
FYI he is not married, they were partners or bf/gf. She's been wayward still since before they broke up, and they obviously live together and have children.
Helpme, when did y'all break up?
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.