Timing should be low, or if it has actual degrees settings 3-5 degrees will be safe enough. PWM is only useful up to 12khz for most motors as 99% of the motors we use are iron core, raising PWM will not increase performance, only make the ESC run hotter. Make sure the brake is off, set your cutoff voltage to 3.3v minium per cell. 3.4v is better with many of todays hi power lipos.
ESC can be 120A it wont matter if it has no airflow, it will still be susceptible to overheating. Make sure you have airflow over the heatsink.