I think that I want (need?) to adjust my DPI.
Qualitatively, text is very small and I usually find myself increasing text size in text editors, web browsers, etc.
Quantitatively: The 1" square here is closer to 1/2". Using the monitor size reported by xrandr (11.1"x6.5") and my current resolution (1920x1080), I find that my DPI should be ~170.
I modified lightdm.conf and the Gnome text scaling factor as described in this related question, except that if I used the ratio between my theoretical DPI and 96 (1.77) as the text scaling factor (as described in the post), it was unusually big. 1.2 seems much more appropriate.
The text scaling had an obvious effect, and I think that the menu text changed when I restarted lightdm (although I expected a more obvious effect from nearly doubling the DPI). xdpyinfo and Xorg.0.log reflect the updated DPI (170), but xrdb indicates 115.2 (96*1.2, my text scaling factor).
None of these changes affected the square. Adjusting the text scale fixes most of the nuisance of having the wrong DPI, but I would prefer that things are "right".
Should I be doing something else? I tried changing my resolution, but none of the choices looked right.