to answer your scale question, you definitely want to give the face a bit higher scale then your average mesh and you want to give the eyes a lot too, compared to their size, just because its the main focus of the character usually.

For mapping things like the mouth, you'd need to get in there and untangle it one point at a time, no projection is really going to cut it right out of the box. I'd also recomend not having the face split down the middle like that. you want your texture seams to be put in as nondescript places as possible, so the back of the head would be better. Check out the sample face texture I have in my portfolio to get an idea what I mean. (link in sig)