Thank you Charles and John. I've returned to this issue and, with your help, I've got the even / odd page numbers straightened out. I'm almost OK with the running heads, too, except for one section.

No problem on the even pages. Same heading throughout.

On the odd pages the heading changes with each chapter / section. Everything works fine for sections 1-13. Then on section 14 (Appendix) the odd page headings say "Notes," instead of "Appendix." Section 15 is the beginning of the Notes section, so it's picking up the running head for the following section.

I have read a lot of the pieces you recommended about "sections in MS Word" and assume the problem has to do with the fact that section 14 header is being governed by the section break in section 15. But I can't figure out how to fix it.

I don't know if this is related, but I can "see / display" every section (through section 20, the last one) except for section 16, which I cannot find. Right after the Notes section (15) is the Glossary, section 17.

Any ideas?
Thank you both, again, so much for your invaluable help, and your patience.