Mel
you're asking difficult questions once again
But that shows you're thinking hard about your position in your boyfriends life.
I don't think there is one breakthrough, we're all individuals and our breakthroughs will be different - and at different stages.
But it's not unusual for us to suddenly find that something begins to make sense, and it can be very small and seemingly inconsequential things that make us sit up and say "HEY, now I understand!"
You say he's expressing emotions that he hasn't done before, that was a major thing for me I know. I went for 30 years without expressing my emotions to myself or others - especially my wife.
I acted some emotions, and I acted very well. But I gauged what emotion was expected of me and did "that one".
That's a big difference to accepting our own emotional response to something and acting accordingly.
Acting more or less guaranteed that I sailed through life trouble free, because I was lying to myself and accepting things I didn't want.
Does that sound like your boyfriend "accepting" his mother in the past and reacting negatively towards her now?
His present reaction is the TRUE emotion, and he's going to be scared witless about this. It's all new and untried, and only the people ( you mainly ) who know, trust and support him can validate these new emotions.
Don't go over the top though

just be there and trust.
Anger and revenge will most likely be a part of the new emotions as well. But again it's an individual thing what we do with them.
I've never looked for revenge, and I directed my anger into my writing. Some guys work out, there's many ways of 'losing' a bit of anger.
I was reading some of the other message boards, and one person said he has fantasies about the abuse. Is that common? I can't imagine him ever admitting to that, even to a therapist. It is things like that which scare me.
I did it for 30 years, still do very occasionally. But I can stop it when it starts now.
one of the key things to breaking a fantasy is disclosing it, and a good therapist will have heard it all before.
As for you feeling scared of his fantasies, that's understandable, but I don't think it's something that should scare you.
People use fantasy for heightening their sex drive all the time, ours just tend to be moulded from our abuse unfortunately.
They are hard to wipe out, very hard. Slightly easier to .....soften ( for want of a better word ) or reduce. But, just like the whole healing process, being brutally honest with ourselves is the key. If we can also be as honest with our partners as well, then that's a huge bonus.
that's painful for you guys, make no mistake about that. And there have been times when I have caused my wife untold pain, and I was so wrapped up in my healing that I barely noticed. And she, to her eternal credit, never let me see all of her pain. It's only now that I realise what she actually put up with and just how much she supported me.
I have a lot of making up to do!
Dave