Its description says that he cannot spend fatigue for extra movement. Does it means that he cannot use fatigue to move the miniature, or that he cannot spend fatigue to obtain movement points? For example, could he spend fatigue to drink a potion or change items?

gran_orco said:

IMO he cannot spend MP generated from fatigue for movement, but he can spend them for non-movement movement actions. We know from the ruling on 'ending movement' (for example on encounter markers) that most movement actions are not movement.