I ended up ditching the tavern but I have created a building map! I realized part of my problem was that the amount of stuff I'd have to draw (furniture, props, etc) was feeling overwhelming. So instead of doing a tavern, I switched to something that was (to my mind at least) a bit more limited in scope -- a bakery. I wouldn't have to do the furniture for the bedrooms at all and could stick to just doing a kitchen and food items.

Click image for larger version. 

Name:	Bakery1 Day preview.png 
Views:	21 
Size:	1.52 MB 
ID:	134017

I again started with a blank DungeonDraft map as a scale reference, although none of it remains in the actual map. The objects and everything else are all a mixture of DAZ 3D, digital painting, and some photo textures.

I don't know how "limited" the scope actually ended up being, because I kept doing tarts and things. I have more items than could fit in this bakery, so I might have to do another, larger bakery map. But changing the project to a bakery and focusing on the objects first instead of the specifics of the scene did help me trick my brain into finding the project more manageable.

So I guess I've discovered a building/structure map process that works for me, although I don't know that it'd work well for anyone else! I might also try DAZ and Blender to make some isometric maps, but that's just a thought right now.