I think the notes on the set reference is because B had given the girls a note, saying something like, " I don't want to try to replace your mom just get to know you, and develop a relationship." It sounds like I and B follow the guidance of a therapist.
If the MC account is shared, as it sounds like it...that is why Big Al sounds like she is talking to herself. She wakes up and sees what hatred E has spewed and gives it her motherly approval.
I told my daughter, of similar age, about the toddler tantrum and she said it "sounds like that kid doesn't have many real life friends". And the ones she has are probably some gaming online loser friends because young teens don't act out like babies, it would be embarrassing. M'kay? Acting out?sure, but throwing food and melting down because your Daddy has a gf? Nah, m'kay! These teenage years will probably be way harder than normal thanks to stupid Al.