Hi Dan, have you got a ground wire going from the tremelo claw to a common earth point ? (looks like back of volume pot is your common earth point). If you have this and the humbucker is earthed correctly it should be fine. Some of those solder joins for the earth wires may need to be cleaned up and re-soldered. Don't bother looking at the PBG wiring links I don't think there is a diagram for what Andy suggested plus its a 5 way switch. Should have been a case of swapping out the bridge single pup and connecting wires for the humbucker to the same locations.