Daniel, a close shot pic could be helpfull to Mica realize what is going on. I can understand distortion if the preamp is too hot, but that doesn't explain hissing.
Does it have the magnet beads? Alembic PU can be really picky about RF interference and AC magnetic fields, and as we have no rigid control over radio transmission bands in Brazil (you know, all those church pirate radio stations...), they are essential. Until I realize that just one PU was passing trough the bead I suffered for sometime with my Rogue since I play a lot near TV and Radio antennas.
Are you really sure volume pot is original? Because it seems the tapper is wrong (behaves like linear and not logaritmic, as it should), can you spot any letter writen on it (as LOG or A)?
ps. If you want, contact me inbox and I will give you my personal phone number to talk in person and in portuguese (don't know about you, but to me is always a little struggling write in english).