How To Evalulate Correct Exposure

Hello,

I'm looking for a little guidance and just trying to validate my workflow here. I found it really cool that I can mouse over the image and evaluate exposure in different regions. Because I'm shooting raw I should understand that these values come from the camera's reflective meter correct? I'm using a 3D scanning/ photogrammetry technique that requires I shoot on a dark background. Because of this I can expect to shoot an image with a lot of dark value. I believe that my image being primarily black might skew the reflective metering.  My question is, how do I make sure I have the correct exposure on my subject. Should I be using masking to evaluate exposure on just my subject? As I understand it, the correct exposure should preserve information in shadow and highlight areas. But my goal is a completely shadow-less image. I shoot with a ring flash to achieve this. So then I thought, maybe I should use the picker icon to evaluate the darkest and lightest areas of my subject. And I can see for both areas I'm not touching the "goal posts" of the exposure evaluation meter. Is that a correct approach? How can I evaluate the histogram in this scenario? And it's too much black for that green exposure tool right?