Although you make some good points regarding Mīm, Kuru, I think it should be noted that the point in history that Mīm lived in was well after the Elves and the Dwarves met, discussed the Petty-Dwarves, and agreed to stop eating them.
To be serious, although I can easily imagine Mīm's predecessor's inhabited the caves of Narog and Amon Rūdh at a very early date, I'm not sure that we can ascribe to these Pre-First Contact Petty-Dwarves a standard of living comparable to their latter-day descendent.