I would definitely avoid taking big swings at anything, even if it is just your idle screw. Careful doing that, you'll really end up in left field.
Something is keeping the carb from sliding more towards closed though if you really put that many turns on it and nothing happened. You're not directly moving the carb slide with that screw, you're setting an end point. In my case, a collar on the throttle linkage didn't have enough gap and as I closed the carb gap I put the linkage in a bind not allowing the slide to go to its endpoint.
Try some different fuel if you get a chance