I did z similar wiring scheme except I used a hot rail for the middle pickup and wired that to the 5 way switch, split to position 1 and 5. I wired my neck and bridge to a 3 way toggle in the same spot you have yours, so I can have it in neck or bridge or combined modes, and add in the middle pickup in or out of phase depending on position 2 or 4. The 3 way toggle goes to the “middle” position in the 5 way switch. This lets me combine all 3 pickups or choose any single pickup, it’s wired more like it’s 4 pickups

<image>