Loonatik, thank you so much! What you said steered me in the right direction and I was finally able to get all the skin cracks to show up! It actually was really simple. I started out tracing over the cracks like you said, but when testing it in Blender I realized that even the areas I hadn’t traced were showing up better. So I just made my UV map black and white, inverted it, and then adjusted the levels a bit so the white areas were more white. I connected that to a bump node, plugged that into the diffuse’s normal section and everything looks much better! I also fixed my specular map, because apparently it had been set up wrong before.
I had been using MapZone to create my normal map, but I think the UV map simply didn’t have enough contrast because the normal maps kept on coming out mostly one color, even if I adjusted the UV map’s contrast or the normal map’s intensity.
Anyway, here’s a quick viewport preview render (20 samples). I’ve still got to fix the other things people pointed out, but I just wanted to see what everyone thought of the new skin texture.