An unforeseen snag

The past week I've been far more productive than usual; I've been addressing some fundamental problems that had been procrastinated for quite some time. First: generating new fonts that have all the musical glyphs needed for scale names and degrees -- so the book uses proper SMuFL Unicode points. I'll need these fonts to have all the musical glyphs for both the book and when I render version 3 of the youtube videos. I really should unify the branding... in varying contexts I'm using TeX Gyre Pagella, Clarendon, Century Schoolbook, and on the website I'm currently using a Google Font called "Spectral", and for sheet music I've used a combo of Vollkorn, Baskerville, "Old Standard TT Regular", and Lilypond's default "Emmentaler". It's mayhem.

Second: I fixed lots of SVG diagrams so they don't have "stroke" outlines. Those strokes were making certain diagrams look weird.

Third, and most importantly: I did a test render of "Volume 2: The Scales" which was intended to be a 4095+ page book with every single scale in it. That's two pages per scale, with the intent that each scale can be printed double-sided with a recto and verso, like a class handout. Plus some indexes, and a preface. Well that's where things went awry. When the book hit 1015 pages, adding the 1016th threw a LaTeX error: "Too many open files"

$#@!

Well that problem was easily solved with the "ulimit" command, which increases the resource limit for the LaTeX process; and ... tada! the result is 4174 pages, 1,862,267,415 bytes.

ouch. yes that's right, it's a 1.8GB book. Even with all the scale bracelets converted to vectors.
There's no denying that's too big. I can't even preview it in Chrome, which is how I preview the work in progress since rendering happens on a remote cloud server. The last thing I want is a book that no one can open and read.

The sensible thing to do is to split the book in to multiple volumes.
But how do I split it up?
There are two ways I can think of right away:

1) split it into volumes grouped by cardinality. Which means there would be one volume for all the scales with cardinality 1 - 4, a volume each for pentatonics, hexatonics, octatonics, and then a final volume for cardinalities 9 - 12. This feels like a neat separation if you know the cardinality of the scale you're looking for... but if you're looking for "Scale 1203" will you know what volume to look in? There will of course need to be an index... even so, this doesn't feel like a great solution. It's what mDecks did with their encyclopedia. (https://mdecks.com/theuniversalencyclopediaofscales.phtml)

2) split them up sequentially into 8 volumes, like scales 1 - 511, 513 - 1023, 1025 - 1535 ... 3585 - 4095. The volumes will all be the same size, and looking up a scale by number will be easy. The division into 8 volumes will make sense for people accustomed to base 2, which I personally think is elegant (but it might not seem that way to everyone).

Do you have any other ideas?