I don't think there's a limit on the ground power unit(s) being available from the ground services. I've heard of people having the A/C GPU connected and actively powering the aircraft for hours at a time. But they will be removed if the plane moves.
That's right, the TURB mode is for passenger comfort. Because it affects the autopilot responsiveness, I assume it's not on by default as it's considered "safer" to be more responsive under (ab)normal circumstances.
Not silly at all. Keep them coming.