Thank you for the information.
I think I’ve resolved the issue, at least for now. I’ll explain what I did in case it helps anyone else. Experiment and testing is difficult with cloudflare, because it can take many hours before a change takes effect, even after clearing the cache.
In cloudflare, I unchecked minification for for html and css, but kept it for js, and cleared the cache. In WPFC, I chose the html and css minification, and css combine options, but not the js minification options, saved the changes, cleared the cache, and deactivated the plugin. Then, I cleared everything from the site htaccess file except the wordpress code, and finally reactivated WPFC, and checked htaccess to be sure the cache code was written to the file. Then I tested intermittently (in a logged-out browser) over several hours, still with no change. I finally went to sleep. When I woke up and tested the site, the green timestamps were finally there. The site speed score is much improved in pingdom/gtmetrix/webpagetest/pagespeed insights.
The site could still be much faster, so I will experiment some more with different setting combination in WPFC and cloudflare, but at least now I have an acceptable baseline I can resort to.
One thing I’ve noticed is that “first byte time” tends to be slow when cloudflare is activated. CF tech support told me years ago that this is because speed tests “don’t understand reverse proxy.” Can anyone explain what that means, and why it would a site tester like webpagetest.org would show 5-10 seconds for first byte time when CF is activated, and 10-14 sec load time, but only 0.248s first byte time, and 4-6 second load time when CF is in development mode?