I suspect you've already seen this, but for the benefit of newcomers, I highly recommend checking out S. John Ross' Medieval Demographics article. A couple of weeks ago, he mentioned making some revisions based on Crusades-era research he conducted.

A great tool to consolidate Ross' material is available online. Brandon Blackmoor's Domesday Book takes a lot of the effort out of the population-creation process.

I swear by these resources and am using them to populate an upcoming low-fantasy setting.

Don't know if these necessarily help with your specific tasks, but I think you might find them useful to extrapolate values. BTW, you'll find that 135,000 is an extremely dense population for medieval cities, but that's based on real-world values, not fantasy setting demographics.

Cheers,
-Erin