Bear,
Have you addressed the THS' AoA as an independent entity from the a/c?
AoA_tail = AoA_wing/body - downwash angle - THS trim angle.
What was 447's trimmed state nearing the top of climb?
No BEA info but close to 3 deg NU I think.
... would there be any chance of the Tailplane Stalling and dropping the tail before the Mainplane Stalled?
No.
As most people here, I cannot understand the PF insisting on NU inputs especially after the zoom climb. To me, it's akin to pilot incapacitation.