The only thing I can see is that maybe the centre of that switch has become shorted to one of the wires where the insulation is gone - certainly could be by the last photos, but that wouldn't produce the symptoms you are saying.
Considering the sound with the jack etc, is it possible that while you are looking at the switch and making assumptions that as that is the only thing you changed, that must be the fault (which is reasonable), maybe by taking it apart, the wire in the jack socket became disconnected or something, or some other issue further down was caused?
Actually looking at the last photo, did you solder the earth of the pickups to the earth of that cable going through, as if you did it might have melted the insulation inside the metal shield, which would produce the same results.