1) see what side of the film the scratches are on, base or emulsion. If emulsion side, it's not the pressure plate.
2) inspect pressure plate and rollers for imperfections.
3) could also be in the felt trap on the film cartridge and may not recur.
4) not sure, but likely Nikon would replace the whole door if plate was scratched.
5) if it were mine, I'd advance a fresh roll through it to see if I could duplicate it.