If you have the lockout tool installed, the input shaft "can" be rotated 360 degrees or more (I initially thought it would only turn 90 degrees before a stop was hit).
There really is no way to know if the shaft of the valve is sheared. The indication from the actuator switches for open or close might be working fine for the cockpit indication, but if fuel can't be moved in or out..... sheared shaft.
Stab trimmed to full aircraft nose down (stab leading edge up). If ANYONE is going to be in the cockpit, tag the trim switches and pull the hydro breakers. If it's crew, make damn sure they understand where you're going to be laying and not to dick with anything flight control or hydro related. You stand no chance if that stab were to move down.