No worries! As for sub-surface scattering, don't let the fancy sciency name throw you off: It basically just means places where the light shines through the skin and makes it look more red because it's shining through the blood in the thinner parts of our bodies, like ears and hands. It's like if you hold your hand in front of a flashlight, your hand looks really red because parts of your fingers are thin enough for the light to shine through them.
Like this:
Or this:
As for the character sheet, the rules "Squeeze everything onto this one sheet," but I don't think they mean that literally. You need to show you work, but not every single step of your work. Show enough to demonstrate that you went through the process, but not so much that it feels overly busy and noisy. I found it especially helpful to look at the character sheets of the five 2D winners from ArtWar 1: Doing so convinced me that I didn't need to render out my character front and back view to the same exacting degree as my main illustration, just enough to make it look good.
I didn't want the light to be too glaring ya know?
I think that you need the rim light under the chin because you've got a strong light source under it, so it should be accurate. But you've seen my entry, and it's fair to say I'm of the leaning that if you're on the side of Light then put light EVERYWHERE!!! So take my suggestion with the grain of salt it deserves! 
