I'm finding Ken Mierke’s explanations of running biomechanics on eveolutionrunning.com to be absolutely fascinating!
Apparently in trying to correct my running form, I've made several new mistakes.
(1) Overcompensating by going from an insufficient forward push to too much of a forward push, and (2) slowing down my cadence to allow for the exaggerated forward push. All that's needed is a short, well-timed, push, and the 180-182 cadence is important to take advantage of the elasticity in our muscles. But also I was trying to generate propulsion with (3) my lower legs and (4) with my feet. Maintaining a constant knee angle through the foot stroke is needed to place the work on the more powerful glutes, rather than on the smaller hamstring muscles. So it also seems logical that flexing my ankle during the the foot-stroke would explain the muscular fatigue and soreness in my feet, achilles, and shins.
It still blows me away that all the muscles can work together so efficiently and so synergistically, that a little 20% effort by our butt muscles provides all the energy we need for forward propulsion!