I've found a document on GameFAQs that could end up being very helpful in determining how to go about doing simulations. It's a
maximum population guide, but it could be very useful because it has an
extremely in-depth analysis of how the population part of the sims works. For example, it has a table of supporting structures (i.e., structures that feed people). Apparently, those purple buildings in Fillmore are mansions. They can support 72 people each, in contrast with 48 for wheat fields and 32 for corn fields. This seems to support my hypothesis about the Fillmore people no longer needing wheat fields when they're at a high enough civilization level. In fact, the author explicity states this sentiment a little later. I will be reading the whole document before I redo the Fillmore sim. At a quick glance, It looks like it has a lot more quantitative info than most FAQS. It touches on all sorts of elements of how population works that most people wouldn't notice, such as the soul counter system, and how the scores you get in the action segments actually influence the maximum population you can get. I'm not sure just how much of this will actually apply to a TAS, but with the depth of analysis in this document, there will probably be some applicable info.
Sir VG: The FAQ was very recently submitted to GameFAQs. It was submitted on March 14,2007, after you submitted your latest 1:10:06 SDA run. If you ever decide to try and make an improvement, I would suggest looking at the guide now that it's available, because it looks really detailed.