The lower tone control places its cap in parallel with the upper tone cap when the lower pot is at "10".
The signal returns meet the 400VDC, which is attached to a ring under the Ntone, and it all goes to the CCW terminal on Volume.
I don't think so.
The pickup signal returns are connected to the grey node which is connected to the back of the volume pot which is connected to bridge ground, which is under the upper tone pot connecting it to the shell and threaded shaft of this tone pot, which is connected to the back of the lower tone pot.
The tone caps are connected to the pot backshells. They should go to the signal return, which is jumpered to the pot backshells.
The only thing that that isolationblocking cap is doing is loitering aboot, and not very well either. There is no AC isolation, DC blocking, nor safety enhancement as it is shown.
Regarding the hum, do these pickups including a RWRP middle, or are they all the same phasing and magnetic polarity?
Funny, I just found a diagram of what I was going to do (QTB / star ground) before I found the Free neck on. It was just fine.
I'm not sure what I was thinking about after I found the free neck on ... I think I tried to amalgamate 1) QTB / star ground, 2) the free neck on, 3) the "This could blend in another tone cap across the neck pot's cap" bit, and 4) a misread of the "Blocking Capacitor" thread ... etc, etc, etc (actually, no etc, etc, etc, come to think of it ...) and ended up confusing my ownself (easily done).
Anyway, I've currently wired it as stock - just to see what I have (it was not correctly wired before I got it ... or after I got it, for that matter).
Oh! and, yeah! I checked the pickups the moment I opened it up. There was no RWRP, so I flipped the magnet and reversed the wires on the middle one before I ever did any of this. That part of it is fine now - good call, by the way.
It's a 1992 Peavey Predator, and I have to say that it's quite a nice sounding guitar, and nicely built and nice looking, as well - I really like old USA made Peaveys. Although it turns out the pickups are just a bit noisey, even in stock wiring - not intrusive, but certainly not silent.
I'll keep you posted when I get around to having another go at it.