DRV8428PRTER Operation Principle

1. What is the full-scale current that is mentioned in the datasheet? Our understanding is that this is the pk-pk output current, that is given as Ifs=Vref/3. However, our results don't agree with this: 

Orange - Input PWM 
Yellow - Output Duty Cycle 
Purple - Output Current 



Ifs was set to 80mA, but we measured 90-100mApk-pk voltage in our test. We noticed that the measured Irms was around 80mA when load was applied to the motor. Could it be that the Ifs calculation (Ifs = Vref/3) is actually for Irms? Also, what is the guideline to properly measure our output current?

If=250mA, 70% duty cycle:  

90% duty cycle case is similar to the first two.
 
3. How is the acceptable range of the input PWM duty cycle determined? In our tests, at 80mA Ifs, which was achieved by 7% output duty cycle set by the motor driver (first image above), the input pwm duty cycle set up to 50-60% worked well. However, at 80% duty cycle, the output waveform was distorted. Is there a guideline regarding what should the input PWM be set to?  

Thanks!