how to adjust the chock/throttle screw on a 2cycle snowblower so it will turn off with the key?

Answer 1

On this planet no choke/throttle adjustment will produce your desired effect!!

Answer 2

Key switches normally work by grounding out the ignition system when the switch is turned off. I am not familiar with your particular machine, but I have never heard of a switch that work that requires a carb adjustment of any sort.

Answer 3

If your machine keeps running with the key off it is most likely a wire come off either at the switch or near the ignition module. Most machines turn off the engine by grounding the ignition.