Muliplying by 64 and dividing by 256 is equivalent to dividing by 4.
Dividing by powers of 2 is easily done with shifts. To divide by 4, right shift two places (>> 2)

And.. the HPWM command in PBP is limiting. If you write directly to CCPRxL, and CCPxCON4:5 you can get PWM frequencies that are easy to filter with an L-C network + Schottky diode (above 100Khz is easily obtainable). That way, your motor sees nearly pure DC. A lot of brushless motors really prefer not to have a "chopped" power input.