Can prolonged sitting on a toilet everyday reading exert enough pressure to cause hemorrhoids or anything else long term?

NO: Should not unless you have chronic constipation for which you are sitting on the toilet for long period.

Sitting on toilet: Sitting on the toilet for prolonged period of time waiting for a bowel movement is like putting a tourniquet around your hemorrhoids, so they engorge with blood and then become symptomaticc when passing the stool. For the same reason i discourage sitting on those inflatable donuts when you have rectal pain. Use a broad surfaced bed pillow rather than the donut if needed. Indeed if your are constip.