Yes...the idle screw adjusts the opening in the carb...leave that one the way it is for the time being...

The screw in the end of the throttle arm is your low speed mixture screw that controls the mixture from idle to about 50% throttle...start out with it about 2-3 turns out from full in and the you should be able to adjust from there..

As for the servo...like Chubsdad said...you need to have the controller AND the electronics in the truck turned on...set the throttle trim on the controller to the center (neutral position)....then put the servo arm back on so it is not pulling the throttle open.