Ideally, the dummy coil should have poles, but no magnet. You want the dummy coil to pickup noise, and poles help. If you add enough metal to the dummy coil, you can wind it less than the pickup coil. This helps the tone situation.
The easiest way to wire that switch is to hard wire the dummy coil in series with the pickup. At the point where the two connect to each other, attach a wire going to your switch. The other side of the switch will connect to the other wide of the dummy coil. Close the switch and the dummy is out of the circuit.
You only need a SPST switch.
Now you have to decide is the dummy is between the pickup and ground, or between the pickup and hot. I think I'd put it on the ground side of the pickup.
Also, just to nitpick... the dummy coil does have to be RWRP, all you need is to either flip it upside down, or wire it in reverse. Humbuckers don't need to be reverse wound.
Also it can't be RP (reverse polarity) since it has no magnets.