Your heater fan should run all the time not just when the heater is on.

You want to aim for 65 - 70 degrees C at the head.

That temperature needs to be stable all the way inside the cabinet so make sure you have enough air movement to achieve constant temperature.

It is easiest to use the heated bed output for the control. The PID controller built into the software should be capable of maintaining the temperature within appropriate limits.

I used a portable hair dryer that has a 500 watt output but I rectified the mains feed to it to lower that by about half. The motor in that is a 12 volt DC motor run directly from the 24 volt power supply with a DC-DC adjustable converter so I was able to minimise the power the motor used yet adjust for enough air flow.