"Which memory item did the PF potentially revert to when he recognized they were out of the flight path"
The two copilots had only been trained for the emergency maneuver at lower levels, in the course of which the pitch attitude to adopt is 10° or 15°.
Is buffet associated with Stall possible in Normal Law?
No, not on the Airbus aircraft.
I do not recall discussions about stall warning triggered at 2 h 10 min 51.
That is correct. From the CVR:
2h10min51,4 SV : Stall
2h10min52,0 SV : Stall
Neither of the pilots made any reference to the stall warning, neither of the pilots formally identified the stall situation.
When the Captain entered the cockpit, he stood behind but between the two pilots while he quickly scanned the situation. He got only general verbal information from the PF & PNF, so he had few clues to go by, including the position of the side stick of the PF. The one thing he did have a good view of was the trim wheels position. Normally they bounce around a little but the THS had moved to the full up position responding to the trim system and stabilizing the aircraft in the pitch axis. There was quite a bit of detailed discussion in previous Threads about the aerodynamics of the situation AF447 was in and the effectiveness of the elevators at that point. Throughout the flight, the movements of the elevator and the THS were consistent with the pilot’s inputs.
The biggest clue given to the Captain came too late: 2 h 13 min 40
PF - "But I’ve been at maxi nose-up for a while."
Captain - "No no no don’t climb."
PNF - "So go down."