Correct.

You could edit the template behind the maps instead, that would affect all future maps made from that template, but not existing maps.

Seems to be an error with the .symfill files themselves. I've alerted the appropriate individuals.

One way you could approach it is to decide the size of the average house. A medieval or earlier house for commoners were usually a tiny affair, often no bigger than my living room. Then, based on your house size, so you can used that against the sketch to determine size.

Lurkers are always welcome too, but don't hesitate to jump in if you have any questions or a map to show off or get criticism on.

With the exception of Symbol Set 1 & 2, you'll find the entire list in the Tools menu -> Add Ons

Only way to check SS1 and 2 is to go into the new map wizard, and under overland and dungeon respectively, see if you have templates for these.