OK, then you need more total movement from your servo to the drum.

You say your radio has end point adjustment? And it's got an "over maximum" ability that comes into play when the kill button is pushed. If you're sure the kill button actually moves the servo a bit more, then give that end of the movement a head start. Adjust your linkage from the kill position.

Move the throttle to closed. Now loosen the lock screw. Now push the pushrod to where the throttle barrel is closed. While holding the pushrod, press the kill button. Tighten the lock screw and let go of the pushrod. Let go of the kill button. Your radio should certainly now be able to bring the carb to idle and the trim and kill should have the movement and freedom to kill the engine. But now.......

Now your computer radio should have enough adjustments in it to do whatever else is needed. You might need to increase the end point for max throttle. But there's nothing inhibiting that movement. If the radio still can't do it, then move the pushrod out on the servo arm one hole or in on the throttle one hole. If that happens you'll need to do all the above all over again. But you will have proven there is freedom of movement at both ends of the throw, and now you'll absolutely have enough movement to do the job.

Almost every model airplane carb is designed with throttle arm movement that matches up with the average servo arm throw they expect to find paired with the engine.