[AlecS]

Ah, I think I see why I was confused, The initial equation was flipped.
Intial Eq:

(Wf * 2 * pi * r)/S = (40lb * r)/Ts

Eq:

S/(Wf) = (40lb * r)/Ts

This puts actual speed above free speed, and actual torque above stall torque, like you described. The previous version was not giving useful numbers, this one does.

You also need to do some unit conversion there,

If use Stall Torque in in/lbs (21.5);

S = (Wf/(40lb/Ts))*2pi)/60/12

This equation gives ~23FPS, same as what I got above. This number would appear correct, assuming 0 losses and perfect current supply.