Zip ties as a gauge is genius, way cheaper than the real deal.

Ugh, the "folding every signature against the grain since I started" part hit me hard because I did the exact same thing and never once thought to check. I kept getting these hairline cracks along the fold and just assumed my stitching was too tight, so I started loosening everything and the books still fell apart. When I finally learned about grain direction it felt so obvious I was mad at myself for not knowing sooner. Now I always do the tear test on a scrap before I fold anything, it takes ten seconds and saves a whole project. Sorry you had to learn it on a 200 page journal, that one stings.