How to (roughly) calculate torque for cordless drill clutch settings?
yes as you stated You could buy a torque wrench clamp it to a work bench or put it in vise and then go through all of the settings on you drill to get an idea of the torque each setting provides, 

but then you have the CORRECT TOOL FOR THE JOB and would no longer need the incorrect tool ( drill/driver ) for the tasks you are performing.