Sensor on the secondarys

So, who knows what the sensor on the secondarys does? Is it a position sensor like the throttle position?

Sensor sees position of throttle shaft and therefore throttle plates and relates this to the ECU to tell the servo to open/close to get to where it should be for a given moment in time.

The drive motor for the 2nd throttle shaft is in between #2 and #3

No you can't put a resistor (or anything else) in the wiring to trick the ECU into opening the 2nd throttle all the time. It throws a DTC (or at least did on my bike, been there dun that)