Amy, I'm new here, so I don't have much experience, but I know the night is darkest before the dawn. I also know what it is to 'scream back' then feel like you blew it - been there, done that too many times.
I do know from experience that "it's your divorce" is one of the best lines - W about loses her mind when I say that because I just smile kindly, and walk away - and she knows she can't do anything about it.
I started to recommend not keeping kids from H, but I battle because W is starting in with OM, and my kids hate it, so I know how you feel. That's a toughie - I haven't figured it out either.