Hi qwerty. I'm a BS and though I've read occasionally in this forum I've never posted here before. But one thing struck me about your post:
i try to explain myself - but i am not heard - and the cycle continues
^^This, and how you go on to say that she asks questions, but as you try to answer, she interrupts/attacks with another question, and so on.
Just my observation here... there is no answer you'll ever be able to give her that will satisfy her needs. No explanation you can give that will ever make any sense to her or create any justification for what happened.
I think she knows this, that's why she doesn't give you a chance to respond. She's not really seeking an "answer", she wants to be heard. This is a common man/woman thing even in healthy, happy relationships. The woman has a problem, a bad day etc. We vent to the guy. The guy starts coming up with solutions, suggestions, aka answers. The woman gets pissed, and now the guy is confused and hurt.
So often women don't really want answers, we just want to be heard. My XWH had zero remorse and didn't care how I felt. R was never on the table. He walked out to live with OW and never looked back. So I can only speculate what I would have wanted to hear had we tried to reconcile.
But again just speaking as a female, and listening to what you've said about her interactions with you, this is my two cents. Maybe shifting your focus from how can I respond to how can I make her feel heard, will help.
Best of luck. I hope someday she realizes how fortunate she is to have a truly remorseful, loving spouse. Some of us would give anything to have had that.