Alrightie, I tracked it down, thanks for your patience
So the deal is that somehow, when I was futzing around with my displays and all, my X defaults / X resources got hosed, and font settings got set kinda big, but it wasn't being necessarily reflected in "system settings" / KControl. Also I commented out the the fontpaths in xorg.conf that have ":unscaled" in them (I dunno if that made any difference).
Anyway, in Kcontrol once I changed the font settings from what it was (e.g. 8pt for all) to 6 pt for all, and applied it, a bunch of the windows changed, but not all, and not all subwindows/widgets within windows.
So gradually I began to recall how X-based systems work wrt X resources, and went nosing around for X defaults files, and then realized that I have both gnome & kde, and some of the gnome stuff might be particular to gnome, logged out and back into gnome, set up font prefs there to match that in KDE settings, and then went back over to KDE, and forced fonts DPI to be 120, and made GTK fonts (a Kcontrol->appearance->GTK Sytles and fonts item) "use another font" that matched my kde settings, and logged out and shut down X, and restarted X, and then everything is essentially fine....
...except that the file subwindow in gedit is using a font bigger than I want and I suspect that it has an X resource that wasn't tweaked by the above contortions, but this isn't the forum (I believe) approp for tracking that down...
anyway, am happier and system is more usable.