How to improve PMOS off time
The gate capacitance of the device is "holding-on" the MOSFET. This is because the only component trying to turn off the gate signal is a 470 ohm resistor. The time constant of the 470 ohm resistor and gate capacitance (around 1nF) is about 0.5 micro seconds. As we don't know what MOSFET you are using nobody can be sure about the gate capacitance but, it could be as high as 10nF for some devices.

This means the CR time constant is between 0.5us and 5us. Dave tweed has suggested using a proper driver (it will have a push-pull output that can discharge the gate capacitance in a few tens of nano seconds) but another alternative is to raise the top leg of the 470 ohm 15 volts (ish) above the power rail. This then causes the switch off time to be decreased because the "aiming voltage" of the " CR discharge" will substantially turn off the MOSFET in a fraction of the time.