Looking at your city it seems to me that it is big enough that I don't think I would put in all the buildings. I would put in the important ones but not all. Then make closeup maps of the areas that need it. So if your party goes to the "Inn of the Old Sign" but there is no combat in the area just put a dot on the map with a label. Does that all make sense?

Yes more symbols! A uncovered half-track, then one with the 3 American soldiers shooting from it. (a "The Dirty Dozen" reference)

A thought, coming in to this late, is to check the flavor text in the Mistborn books by Brandon Sanderson. Which may point to some detail things to through in.

Volcanic dust on roofs, and roads for example.

I found this web site with a series of aerial and satellite imagery. I thought it would be of interest.

I have seen 1600s maps of Port Royal that show turtle pens that look similar to your pens. If you were to add some big turtles in the water that might work.