Dear Barry,
Regarding question (1), I’ve answered a similar question in my August 24, 2011 post in the forum topic found here: AeroDyn Outputs. The main reason for the offset of rotor thrust is that FAST includes all loads transmitted across the shaft between the rotor and gearbox in the value of LSShftFxa (or RotThrust), including the applied aerodynamic loads, gravitational loads (from the rotor mass and shaft tilt/tower deflection/platform pitch), and inertial loads (from the rotor mass/inertia and acceleration/deceleration). The gravitational and inertial loads cause the FAST rotor thrust output to deviate from the pure aerodynamic thrust.
Regarding question (2), the answer is “yes.” FAST calculates the centrifugal forces and these terms would be included in the inertial loads transmitted between the rotor and gearbox, so, these forces would be included in the rotor thrust calculation of FAST as well.
I hope that helps.
Best regards,