Sorry, if you have not disconnected the NSS & reverse light switch, you have not disconnected all that you can on this part of the circuit. Disconnecting the rear harness does not take this out of the picture. 12v fed from this blowing fuse goes from terminal W on the bulkhead connectors out to the backup lights section of that switch and then it comes back to terminal Z on the bulkhead connectors; both wires are black. It then goes from terminal Z to the connector to the rear harness via a white wire. Any short along that path will blow this fuse.
There is also another black wire that carries the is 12V form the back switch back to terminal C on the bulkhead connections but I can't see where it goes on the dash side. It may be for a backup indicator light on the dash or console on some models.
