Sorry I missed the first part of this, I guess there’s a reason not to just put a synchro transmitter on your anemometer? Have used synchros/maglip quite a bit and I’m not sure about using PWM. One of my concerns would relate to the impact of the non-sinusoidal / step input signal to the receivers, I would worry if they would ‘buzz’ – may only be a small amount but instead of the indicator making (relatively) slow wind-synchronised movements, it might also have a superimposed oscillation to & fro at up to 50Hz.
Resolver ICs to take a synchro signal and digitise it are common, you may be able to find an encoder version?
If you really have to start from a digital signal, then you may better with, say, coupling a stepper motor and a cheap absolute encoder, to a synchro transmitter.
EDIT: just found & read the original 'part 1' so understand you may have a problem getting a synchro transmitter up at the actual windvane location. Would still suggest that you drive the synchro indicators with a proper synchro transmitter; so have a 'master display' which has both an indicating needle and synchro tx on the same shaft, and drive that with a digitally controlled (stepper?) motor and encoder (just using a stepper motor for displays - be they wind direction or speed - will be OK incrementally but absolute start position could be anywhere in 360* so need an encoder OR a reference procedure whenever powered up to drive each stepper round until it makes a reference switch like a slotted opto switch).