RayOfSunshine, you sound exactly like I did, 10 months ago. You'll eventually stop and ask yourself why you're defending her..
Maybe it's the shock right now, maybe it's everyone calling you crazy for still wanting to be with her.. For me, I said the same thing. W and I both had abusive backgrounds, in many forms, I understood. I understood what other's didn't and weren't seeing. At least for me, my family lived in denial of the abuse they put me through and I felt by defending W, I was also standing up for myself too. And there was a part of me that hoped if I could prove what I good guy I was and that I believed in her, this would all go away.
Well, it didn't and here I am a year later typing this out to you. Ok, so you went through what she did, sorta, like I did. Ask yourself what made you different? Why didn't you do what she did or is still doing? Everyone liked and loved my W too.. best mother, best friend..
Give yourself sometime. I guarantee when you can step away a bit, you'll see plenty of little things that should have added up to big things that you overlooked for one reason or another. Sure, nobody's marriage is perfect, but I bet that you felt that, like me, because you loved her, it would be enough.
These things don't happen for no reason. No, at the core it isn't their fault, but their choices are theirs and theirs alone. It's up to my W to fix herself, that's why I say I'm not standing for her, I'm living for me. It's her mess. I didn't do what she did, she can have it or work to have me back. Either way, I'm not stopping and I'm sure as hell not looking back.