You'll probably never get those vendor extensions to validate since they're not technically part of the valid specifications ("hyphens: none" IS part of the spec).
That said; if you feel you need to control hyphenation at the book level like that, then I would just ignore the warnings.
Just know that many probably won't be happy campers when they open your ebook in their favorite reading app and their decision to enable hyphenation is completely ignored by your book.
