I've got this working, though it's a kludge. One of my goals here is to eliminate the need to break documents up into chapter files, so I can't use <$chapnum>.
For the chapter number, I have a background text frame with a Running H/F variable defined as <$paranumonly[ChapName]>. The ChapName autonumber format is <n+>, character format Hidden. The Hidden character format is 1 point, color white. This works OK but I'd prefer to actually suppress the ChapName autonumber if there's some way to do that.
