I commented on the video on YouTube, but just in case you don't read the comments there, I'm adding it here as well due to time constraints. The sooner you read this, the sooner you can fix the book before it goes to print:
Could you please, PLEASE, fix item DC? They should all scale based on the Standard DC table, and all items made with infused reagents should use class/spell DC. It's the main house rule I always use and it's SO MUCH BETTER. It improves quality of life dramatically (you don't need to keep looking up items every single time you want to use them, and they remain useful for more than one level of gameplay) without affecting game balance at all (the effects don't change, so they still aren't particularly great as levels increase). You could even put a small box labelled Item Save DC on the first page of the character sheet for even easier reference. This is the one change I've asked for since the 2e playtest and the one thing you've constantly ignored, even though it's objectively superior to what exists now.
The only thing it affects negatively is the Toxicologist, but let's be honest here, that research field is an absolute pile of hot shyte and should be removed from the game entirely.
Also, why do Celestial Magic and Fiendish Magic have different prerequisites? The former states, "... or another lineage feat associated with celestials," but the latter doesn't have something similar with regards to fiends. The first PF2e books had similar inconsistencies all over the place, so please comb through this release as best you can to try to avoid them for the remaster. I'd honestly suggest just releasing the books on PDFs to the community so we can help. Crowdsourcing is really useful with this kind of thing.