Curious, is it fairly normal to be selecting descent rates like that in good visual conditions?
I can understand initially setting something in, but then haphazardly changing it on final? Perhaps I'm a bit naive, but I would have assumed one would fly the yoke at that point if the plane starts to get significantly off of GS, not mess with a descent rate. It seems he could have caught the whole problem a long time before having to cut to idle, and the the auto throttle misunderstanding that followed.
EDIT: after thinking about that point another moment, I guess the auto throttle would be coupled to what you selected as a descent rate. So perhaps if he didn't want to hand fly, that is the only way to keep the throttles where you want them?