I believe the question difficulty relates to the singular question whereas the PSG/Game/S difficulty refers to the difficulty of the overall passage/game/section. So, the difficulty for this passage is a constant value while the singular question difficulty varies question to question.

Same! I didn't see the author's recommendation for empirical research as a change to the current methodology used by the specialists but rather as a new or different approach, which helped me eliminate D.

Got this super easily! Yay!