It's painful to watch but I think necessary. And clever. He is going through events with a sort of linear progression, but then pops back and forward to go over things in an out-of-time sequence which would be next to impossible to keep up with if you were lying.
I tend to think he didn't know it was Reeva in there. I can't believe, for one thing, that they would have argued for what would have been several hours going right up to 3am. They don't strike me as late night types. If this had all happened at 11/12pm it would make more sense. I think he is emotional because he knows that what really happened IS incredibly far-fetched and he knows how close this is all going to be.
Reserving the right to continue to sit on the fence however... 