I think the State Dept. site says you can apply for renewal 9 months before?
That's their suggested time for renewal, but I don't see any prohibition on renewing it earlier. In fact, those who run out of pages for visas
must renew their passports now that they've stopped issuing extra pages, and that could be years before expiration.
No, you cannot. Applicants who need additional pages in their valid passports must obtain a new passport by mail. Applicants within the United States may choose a 28-page or 52-page book.