Here's the final update, at least for now.
I spiked up, hit the track, and ran 5:12. My splits were reasonable (76 for the first 409, 2:35 for the first 809, 2:37 for the last 800). I didn't have much left at the end. 5:12 is about as good a mile as I can run right now.
So what did I learn from this experience?
o Daniels works. Daniels phase IV was worth 8 seconds for a mile, which is pretty significant.
o Running 800s at mile pace in workouts sucks.
o 6 x 400 at faster than mile pace takes me longer to recover from than 14 miles at marathon pace.
o I age-grade at 80 in everything from the mile to the HM
o My last chance to break 5:00 was in 2013.
o Racing on the track is fun and more people should try it.