if you have the time model it... but creasing is faster and easier to handle... for games (baking) and featurefilm... for example the falcon model in the latest starwars is all creased...
Concentrate on the structure of the face. Get used to using the trimdynamic brush or flatten brush to define your face planes properly. Here is an example image:
Long thin faces will cause this too. For example a curb on the side of a straight street... if it's not divided regularly, then it makes two very long thin triangles.
IIRC, in that example 'Rho' is a constant that represents something like specular intensity, for which you probably could (and probably should) indeed use a texture :)
I think that you should probably redistribute some of the polys that are at the back of the head to someplace more useful. The chin, for example, seems really sharp.
That should be doable with a custom shader. We already have shaders that only show the tangent, normal and binormals for example. You can look into those.