[Daryl]

Why is JB's right palm up at both address and impact?

I see it at Impact but its questionable. I wish there were a better video with a close up.

Why does it look like only #2 accumulator release before impact and @3 no release until after impact?

I think you're correct. He Uncocks and Swivels his Left Wrist before Impact. He should Hinge through Impact but it looks more like a Flip and Bent Left Wrist from the birds eye view.

If there is right arm thrust from his swing can it be other than with a pitch motion if the right palm remains up?

It looks like he hurls the Right Forearm Flying Wedge through Impact. Like skipping a stone across water. No doubt that its accelerating from a Pitched Elbow.