320p
1. Perhaps the lack of slats affects the airflow over the elevator - the higher than usual speed compensates.
2. Yes it is unusual but that's what the book says! Presumably Airbus tried it the "normal" way and did not like it...
3. A lot depends on the a/c weight, and the pilot's handling skills in Direct Law - I would guess it is a dynamic stall warning, unless you are allowing the a/c to decelerate rapidly once the gear is down. Best to stabilise the speed not below VFE NEXT - 5KT until the flap has reached 2, then decelerate to take Flap 3.
And the stall warning is only doing it's job - I would only worry if you stalled the a/c!