I liked the Jan 21 head enough to attempt a retopology on it. This, being a terribly analytic process, revealed to me many mistakes I'd made in proportion and shape, which I proceeded to fix. This is version two of the same head sculpt (not the retopology). While I don't claim it's perfect, I am much happier with the facial features in general. I also spent much more time on the ear, with which I am extremely pleased.
The retopology is well underway. I have wrapped the whole head except the ear, which I will do next.
I find head sculpting and retopologizing fatiguing, yet extremely rewarding.
I'm extremely glad for @theluthier's Creating a Realistic Human Head series on YouTube, even if I do slow it to 50% and make him sound like a dizzy sloth.
Suggestions for improvement are welcome!