I think I'll answer those ??'s in reverse order:

3. What does the rotor stop screw do?
The rotor stop limits the lowest throttle setting possible. Ideally you want to be able to fully close the carb in order to be able to kill the engine remotely. Back off this screw until you can close the carb.

2. When I go full throttle I'm getting a little hesitation... sometimes a stall. I correct that with the needle valve right?
Does it sound like it's "burbling" (to rich) during transition? This should improve once you have the high speed needle valve and air-bleed set correctly. It is probably to rich at idle.

1. I'm trying to tweak the engine. I set the idle speed with the air bleed screw correct?
The idle SPEED is set using the carb. The idle MIXTURE is set using the air-bleed screw.

Set the High speed needle valve for optimum RPM first, then richen it up by a couple clicks. Now adjust the air-bleed screw (and carb) for a reliable idle with smooth transition to high speed. Once the air-bleed screw seems right, re-check the high speed needle valve, since the air-bleed screw also affects the high speed mixture slightly.