He also said if I can't handle him snapping at me now and then (which as mentioned last night, wasn't actually the issue for me) then I was pathetic and there wasn't any point in continuing.
And this is where I wish you could just say, "Hey, you know what, I'm pathetic! Let's give up."
Why should you "handle" him snapping at you when you could be either on your own or with someone who doesn't snap at you (my now-DH never snaps at me about anything)?
@reader12 is right:
your longing to untangle and understand everything before you act could keep you trapped for a long long time. But you don’t have to be certain of being “right” or justified to leave. You can give yourself permission to leave because you know in your heart that you will never be happy with him. That's enough. You don’t need any other reason. That’s all you need to know, and you already know it.
However, I have a feeling OP that you just can't take the idea seriously. It's brewing in you, but it needs more time, and only you know how long you consider "sensible." It might never come to anything. Or it might, in another 10 years' time, or perhaps later still, e.g. when your daughter has left home. Or maybe never!
It seems that you strongly believe that the only fair and sensible thing to do is to stay. You would never forgive yourself if you "gave up too soon," which means making every effort you can to smooth and soothe. And because your husband is keen not to let you go, and because you are used to being treated badly, it won't take much for him to hang onto you.
There's a narrative about Hiroshima, along the lines that only something on that inhuman scale would allow the proud Japanese to give in without losing face. (I seem to specialise in tasteless metaphors, sorry!) Maybe you're waiting for your personal Hiroshima so that you can point at it and run.
Based on my own experience, I'd say the trouble is that when something massively traumatic like that does happen, you go into shock and your first impulse is to restore normality as much as possible. Then months, perhaps years, go by where you are not inclined to take any action that could make life worse. You retreat to lick your wounds and get your breath back.
By the time you start coming up for air again, you find yourself in a situation where you're thinking, "Well, I can't possibly leave now because I didn't when the atomic bomb went off, and nothing will ever be as bad as that, so it would not make sense to leave now, or indeed ever."
This is the trouble with forcing your life to be driven by logic.
But I understand your need to behave logically.
Especially when you have adapted to completely discount your own feelings.
Just be aware that being expected to behave logically is not as important in the "normal" world as it is in yours.
Being with someone like your husband, because you're permanently standing to attention in a courtroom, makes EVERYTHING in life unacceptable unless it follows the laws of his logic. And the laws of his logic are built to serve his interests. (How many arguments do you ever win?)