Heh!! Isn't experimenting fun! It's good to keep a punching bag near by so you don't have the urge to throw your tools through the wall or window...
Very cool on the motor RPM display! This is going to be very useful for you when you experiment with bb ROF and motor speed efficiency.
Well done!
Only thing that I can tell you, and I said it before (long before you started all this) is that you should expect that as the motor speed increases, you will still get "air shots" to increase. Nature of this mag design is that bb's will get flung from the auger spring. To minimize this, keep the mag as full as possible. Weight of bb's in the reservoir will help keep bb's in the auger.
If you want to see a demonstration of this effect, put about 40 bb's in the hopper and look in there when you activate the mag motor.
Anyway, I look forward to your testing. Good luck!
---Cam