You and your sibling are treated differently because it sounds.as.if the sib is enabling your mom. Blackouts are no excuse for abusive language. Trust me the things your mom says to you are abuse. You also dont owe your mom anything. As a parent it is our responsibilty to do as I think it was the Dhali Lama who said it
" Give your child roots to grow, wings to fly, and a reason to come back". Or something like that. No contact is hard. You will possibly mourn, feel guilty, get angry and a whole lot more. But, I have yet to meet anyone who went no contact that ever regreted it.