Spent some time today browsing old posts on The Art Department, reaffirming my sense of proportion. It made me strangely optimistic, because, basically, there's nowhere to go from here but up.
I fooled around with the shadowed edge of the face tonight, looking for the correct placement. Some bits are better, I think, although the area around the eye is still off. I've also got to find some way to soften that expression.
Based on comments on the last post and some of my own ideas, I tried to put some separation between the two parts of the picture. I used some semi-abstract overlying shapes, as well as letting the two parts overlap where it seemed necessary. As Hasa suggested, reducing the area lit in the neck area did seem to help the composition.
I may have to call it a day on this one soon.