How do I adjust these colors Vectorscope YUV?

This looks like a pretty solid color though I'm suspecting you may have video noise in the sample. Which would account for the tiny amounts of cyan/blue. 

Have you moved the mask a little to see what results you get?

To make a selection like that is called a secondary selection. A primary selection affects the whole image, a secondary selection is "qualified" to adjust only a selected part of an image.

So ... in Premiere, that's the HSL Secondary tab. And set the key to those specific hues, maybe a hue-only selection with luma and sat turned off ... you'd have to test of course. But I don't think it's worth the time.

And I work for/with/teach pro colorists, work heavily in both Resolve and Premiere. The only times I've seen that sort of trace have included video noise.

I have a thin line darting toward green and another thin line going toward in between cyan and blue. How do I get those two thin lines to join the rest of the colors that are near the skin tone line?