I think every ding in both the leading and trailing edges will cavitate. I would at least deburr it real good with a file while you got it apart
The dings and poor shape of the impellor don't cavitate, those conditions create cavitation.
You have to remember folks that water is roughly 1,000 times more dense than air. Tolerances are critical in a performance pump.
I guarantee that pump is cavitating. Grinding and filing on the leading & trailing edges without taking into account the balance of the impellor is not wise.
What are the clearances on the wear ring to impellor? Has that cavitation and vibration caused wear on the thrust bearing or the tail shaft bushing?
I spoke with jgrocha ten minutes ago. I know Chris at B1 will be able to steer him in the right direction.
Carry on.
Dave