It isn't like there is an official definition, but my interpretation is that anyone born in Korea can consider herself and market herself as a Kgirl. This applies whether her current home is in Korea or the US, and regardless of her citizenship visa status. I have known Kgirls visiting from Seoul for a couple of months, Kgirls who living permanently in the US with green cards or US citizenship, and other permutations in between such as student visa.  I don't think agency versus independent matters at all and the progression from agency to independent is a common one.

Ethnic Koreans born in America are more of a gray area, but I wouldn't have anything against it. Also, some people are marketed as Kgirls who are Japanese or Taiwanese or pretty much from anywhere in NE or SE Asia from Singapore up through Japan. Again, I don't have a problem with that, although the actual ethnicity and language abilities should be disclosed on the website for people who do care.

To me, Kgirls are Korean girls that work for a Korean agency. Kgirl is not just about race but the whole kgirl experience including incall and routine.

You would be classified as an independent, of Korean descent. Again this is just my POV

Generally kgirls don't charge as much as you do and offer more on their menus than you but also don't keep as much of the money. So I don't know if you would want to market your self as a k girl

I always think of K girls as a term for Korean born girls vs Koreans  as a whole

I think at your price point in general is higher than most K girls.  It would be marketing yourself "down" in rate