How to correctly calculate load on a DC motor
The free running current accounts for the countertorque coming from commutator friction (mostly). This torque is always there and so this free running current is. If you have additional friction in your drive, e.g. from a gearbox, you have to add this to the free running current. Or simply measure.

What "30% load" means depends on your definition. Is it motor load, needed for example for sizing the other electrical parts? Then 1st solution is correct. Or is it the additional load you may connect at the drive axle ? Then 2nd solution is correct.



You calculate the load torque from the drive current and the motor constant Ki. Voltage doesn't go into that equation, that one is needed for calculating speed and power one step later.