I can't remember if you've posted before about your fuel pump so maybe this will be repetitive.
If it is a brand new pump, I'm inclined to believe that the fuel pump is faulty. Modern fuel pumps for the 216 and 235 (and virtually every other old car) are all Chinese garbage.
See if you can locate an original pump or one re-manned 30 years ago or so and have it rebuilt.
Many people on this site, including me, have had this experience caused by the crummy pumps available today. In my case, two of them failed - one of them straight from the box. Since I had my original pump rebuilt by Then & Now Automotive, I have not had any problems in over 4000 miles.
By the way, I use 87 ethanol virtually exclusively and haven't encountered a problem here in 95+ degree Atlanta.
Test your pump's fuel pressure and its output. One or both is likely incorrect.
