luzluz, what you say about all the different levels your mother operates on really resonates with me.
My mother is sort of OK in her day to day persona, and like yours has very occasionally recognised the truth of what I say and what really happened in our family, but she is incapable of sustaining that awareness. It is literally too much for her.
And if I push things, and refuse to play along with the charade that we're a wonderful, warm, loving family and nothing "that bad" ever really happened - if I won't sacrifice my own needs and identity in order to make her feel OK, as I was always expected to do - then her everyday persona disappears and the bully appears, shrieking away like a demented chicken, making herself out to be the victim and the martyr, and generally furious at me because I won't obey her.
I have been NC with all my family for some years now. It was very hard to do - still is, I won't claim it's easy or that it made my life loads better overnight - but I really felt I had to do it for the sake of my own sanity and self respect. The bullying and EA in my family came not just from my mother but from my father and only sibling (older brother) too, and three against one is just too much. I continue to stay NC in order to protect myself and my own family; as others have said, I have to put my DC first, and myself.
I do however mangage to maintain a relationship with my niece and nephew and have done so for about six years now, since they were teenagers and old enough to travel to see me by themselves. They are now 21 and 19 and last week my niece phoned me to tell me her degree result within 20 mins of finding out herself, and I like to think that says something about the relationship we have.
It is very, very hard to keep up, and it nearly kills me sometimes - the fact I am estranged from the whole of the rest of the family is plainly the elephant in the room - and I do wonder sometimes how long it can reasonably go on like this, but for now it's just about working and DS loves seeing his big cousins, albeit rarely.
I know a niece and nephew are very different from a DB, but I've included this just in case it has any relevance to you re your relationship with your younger brother, seeing as he too is now old enough to have an independent relationship with you, if that is what you wished. But am not trying to push going NC on you! It's such a huge decision and although some things are similar, each person's situation is actually different. I don't think there is ever one universal "one size fits all" solution.
Totally understand your need to rant. Ranting is good 