Is this circuit for Piezo Transducer and corresponding resistor values correct?
If the piezo speaker only draws 5 mA at 4 kHz when driven with a peak positive voltage of 3 volts then there is no need for a current limiting resistor if you are driving it with a peak voltage of 3 volts.

On the other hand, it might be a good idea to have a series resistor to prevent the instantaneous current draw from the MCU pin exceeding limits stated in the data sheet so, focus on that and not the speaker.

You don’t need a parallel resistor to discharge the piezo speaker capacitance because when the MCU pin cycles naturally through a low part of the waveform, it will discharge the piezo capacitance.

Your calculation for R2 is fundamentally misplaced in theory.