That did it – The only caveat for reading order is that in the Title Explorer, the TOC group had to be ABOVE the Nav buttons group in order for it to read correctly. This somewhat contradicts the help information for grouping and setting reading order to last, which I’ve brought up a few times when it comes to reading order with groups.
Also, I discovered a quick trick for “hiding” HTML elements from the screen reader. In my case, there’s a group of CSS files at the title level. I set the group to read last and initially hidden and NVDA never even read them. The next test is to make sure the CSS still applies on elements later, but I doubt that hiding the group is going to impact that.
Thanks for the help, Tim!