Oh my god, I'm sending giant hugs to you.
The only thing I can say is this, and it won't help since your D6 is hurting TODAY, but kids grow up and they begin to see the pattern in what kinds of games the AH is running, and they see how they were manipulated and how their trust and love was abused. I had this very conversation with my therapist last night about my son and his relationship with his NPD dad, and she said that the most important thing I could do is validate his feelings. He is right to be upset, he is right to feel pissed, just like your D6 is mad that her day got ruined! My advice, take it or leave it, is to let the girls know that AH isn't allowed in your house anymore. You can tell them in a way that is age-appropriate and gentle ("daddy is sick, he and mommy can't be around each other right now, we really hope he will get better someday" and if they ask why/how, use the other night as a great example), which will keep all of you safer and prevent him from tricking the girls into bending and breaking the rules he's too stupid and reckless to follow.