Frida - the big heart. Well, she is nuts, but I think she was trying to do right. She cared - in so much as she was/is a real worrier (neurotic let us say), she cleans, she keeps order. She made us look smart. She shouted us into academic submission (we all went to Oxbridge). We all had anorexia... I had no idea family life could actually be good before I met my OH.
I relate to your comment: "One of the things that took me years to get my head around was the fact that she was never going to wake up one morning and be the mother I deserved". I am really trying to accept her for who she is. It's so distressing though, isn't it. And springy that thing about arrested development is interesting.
Who else had a mother who demanded respect? That believed her way was the only way? And yet did the most disrespectful things?
Internalising the things she said to me (including constant threats of suicide after drunken episodes) really robbed me of my childhood and 20s. THAT is really hard to forgive and forget. But I realise, like the OP, that I don't want to spend my life under that shadow.
So I know I have to move on, detach, ignore, and as frida says accept I got a bum deal. See, I feel guilty even writing that...she honestly thinks she has done the best by and for us. She is devout too. In fact, any of our successes or kindnesses are, to her eyes, proof of her success as a mother. 'Look at you all: I must have done something right!" We're OK despite, not because of, a lot of things she did. Although again, I feel disrespectful writing that since she did give us many opportunities and she was always very kind and accepting of maligned, minority or disadvantaged groups - whether foreign, disabled, or etc.