I wrote the post last night. This morning I opened up meta.Discourse.org (this forum) and the layout looked the same as our own Discourse site. This confused me until I realized that I had meta set to the redditish theme, same as on our own!
Lesson here is that for first-timers like me, and others, if you are experiencing layout issues, check out this here meta.Discourse.org forum, and instantly swap in the various themes like Horizon, Material, redditish, and Sam’s Simple (from selector at lower right). You’ll get new ideas and you can confirm if your troubles are coming from the theme or not.
Thanks again to @NateDhaliwal & all!