1) Based on Pasquale's description of PSI and the PSI booster text (made from "saturated psycho-catalysts and glucose"), it would make sense that eating food would gradually restore reserves. (Maybe only certain types of food?) Sleeping too, although there's only like 2-3 instances of that in the game.
2) It'd be very convenient if reserve restoration was part of the doctor's fee (maybe with the exception of Pasquale).