I’ve made a lot of progress.
First of all, I believe the problem was that the monitor wasn’t warmed up enough and was drifting during the calibration. I re-tried the calibration, including white-point setup, about half an hour later and during white-point setup got completely different monitor settings (lower brightness). I turned off the screen saver and auto power-off and tried again after a few hours and had no trouble that time.
However-- If I successfully generate a profile and then “Evaluate” the profile immediately afterwards I get an average dE value of 7.3, with some individual dE values as high as 16. I repeated the whole process (Calibrate, generate a new profile, then Evaluate) after several more hours and got almost exactly the same average dE value (about 7.3).
What does dE measure?
Is 7 OK or is it high?
What about a dE of 16 on a particular color?