How to operate a BLDC motor?
I think the most common causes for burning lowside mosfets are: missing deadtime in PWM mode or errors in commutation tables.

What I would advice:


Make a simple commutation table in a switch case without PWM. Just to check that the motor will turn and your electronics are correct (voltage and current should be limited by using an lab power supply). Or don't connect the motor and measure the gate voltages with a multi-meter step by step.
Be sure to do the math on the components. Focus on MOSFET turn on/off times, rate of gate charge, max driver current, and max drain source voltage. This allows to calculated a correct bootstrap capacitor value (are you using 22uF? this is way to high).
Start digging in the microcontrollers datasheet to find a way to enable complement PWM with deadtime, if this is not available most of the current will freewheel through the MOSFET's diodes which can be the cause of extreme overheating. So a quick but very dirty fix is adding parallel (with lover Vf) diodes to the MOSFETs.