The animation test definitely showed some of the rig's flaws and fixes.
I corrected the clavicle controls; they weren't working correctly and couldn't hold keys.
I also smoothed more weights between the neck and head.
I locked and hid transformations, rotations, and scale of some controls that I had forgotten to do previously.
Again, if I were to revisit this rig, I would make more mouth corrective shapes, or might redo it entirely using double wire transformers.