I've continued to fool around with this stuff.
After looking at this page with data taken from the UN FAO and the World Bank,https://ourworldindata.org/yields-and-l ... -use-today
I realized that I had just gotten lucky earlier, and what I had called 'habitable' land can be considered to be 'agricultural' land instead.
This agricultural land can be further broken down into 'crops' and 'livestock' ( arable land vs pastures, etc.) where the 'crops' supplies 80% of a world's caloric needs and the 'livestock' takes care of the other 20%. I figure the effective production area based on that and find physiological density from that. Earth's is a little over 400 per sq km.
In my own spreadsheet, I can set the crop area and the livestock area, even if it eliminates other parts of the 'habitable' lands, such as forests.
For tech effects, I set up a sigmoid curve starting at tech 0 ( hunter/gatherer people / sq km ) to tech 15. Advancement accelerates from a slow start and tapers off as the maximum possible is reached. Because I'm using numbers from ~tech 7.5, the efficiency will be 50%; at extreme development, twice as much food/sq km can be grown with resorting to life support tricks. I also guess that the average soil quality is .5 in a range from 0 to 1. On a map, the soil quality is directly related to available moisture, so some areas on a world will be great from agriculture, but other areas will be awful, but balancing out to a .5 soil value overall(?).
I'll figure labor required at each tech level eventually.
I've also discovered how sigmoid curves can model tech acceptance over time. interesting stuff.