I noticed a gray color chip on the Light material room node (Sun), change that to white.  That might be the cause of gray effect when you turn down the intensity of the illumination.  Turn off Shadows on that same light, decrease the intensity, and render your scene.  You should see some improvement in the skin texture with your render.  We'll address using the PhysicalSurface root node later.  I will be away from my computer most of the day until this evening.