To be frank, I can't see your latest efforts. They need to be lit from the front.

(I'd also say, when you're taking pics of dark-coloured minis, make your backdrop mid-shade or dark. The light bouncing off the white backdrop is messing with the camera sensor)
Cool Mini or Not has an article that might be a useful starting point.
http://www.coolminiornot.com/articles/1310-ethnic-skintones
I think it's too concerned with breaking skintones into regions, with some very spurious preconceived notions, and the paint recipes are too dependent on the individuals and lighting in the photos; but the swatches should give an idea of the general colours to use. Have you looked for photos of the kind of skintones you want, yourself?