re: Medieval farmers ate 7000-9000 calories a dsy

Highly unlikely.
By multiples.
For the most part, Europe was starving in the Middle Ages. Not episodically
, but by caloric deprivation. Urban residents often were consuming less than 1500 cals./ day.
This is why disease spread so quickly over large populations, including plagues. People were weak and compromised.
In the Americas, indigenous folks were consuming many more calories per day at that time.