PDF has been around since the earliest days; if Word can't output a clean PDF, why beat yourself over the head with it? As for Scribus, you're really not helping yourself by begging for InDesign, but not making an effort to work with a new tool that thousands of users have found useful. Did a copy of Pages come with that new Mac? Try a test print to PDF with that.
The problem is, by suggesting I throw out all my existing tools, and the stories I've created with them over the years (copying the 'Styles' by definition involves copying over the 'offending' coding), means I'd have to recreate each document from scratch without relying on copy and paste (i.e. retyping everything).
That's a LOT to ask when all I want is to see whether this new publishing site is worth wasting time with or not.
As for trying the same thing on the Mac, as far as I understand the problem, it's how WORD stores their information internally, rather than how it saves it to different formats.
I'll give it a try, just as I'll try running it through Calibre, but I suspect the problem may be deeper than that (i.e. like why WORD keeps track of unused fonts at all!).
If you don't need any design capabilities and you just need to handle PDF and make sure they're clean and functional, you need Adobe's Acrobat. It's the original PDF handling tool.
That's probably my next step, seeing whether I can strip the unused font out of the end pdf, rather than preventing it's being included initially.
However, since ALL the online advice centers around purchasing this one expensive tool--when a free tool wouldn't take nearly as much time, energy or financing--I'm skeptical that none of these alternatives haven't already been tried and rejected.
The fact a POD service requires authors to purchase an Adobe product just to submit a work is troubling, as I've never known any author to have InDesign laying around their office.
WORD has persisted—despite continually griping—because it's a 'legacy' product (i.e. most people have relied on it for decades from their days working for other companies) that it's hard to part with. That's certainly not true for ID!
Rather than chasing my tail, I suspect I'll simply have to abandon my dreams of selling my book to a grand total of 2 or 3 bookstores across the entire country. ::( (That's a 'rolling eyes' emoji).