I hear you. It is absolutely frustrating to see immoral behaviors modeled and poor values enabled. To some extent it's a parenting struggle even while in a marriage with trust and mutual respect, but the problems are certainly magnified in divorce where the children can "divide and conquer". Though my kids are young, I can imagine similar issues on the horizon. Not sure what advice I can give other than unfortunately - like so much of our situations - it's simply out of our control; we have to model behaviors and enforce our values when we can and let go when we can't.
Sorry you're struggling and feeling overwhelmed and frustrated. It is a lot doing the single parent thing plus career and home. So many of us can related. Hang in there. Do the best you can and give yourself a pass on the rest. This too shall pass.
Me:39 Ex-W:37 M:7 T: 9 S:6 D:3 BD/IHS/Confirm EA/PA: Feb '20 OM1 affair ends: May '20 W/OM2 & moves out: June-July '20 W files for D: Jul20 OM2 confirmed: 9/2020 Divorced: May '21