Hi there, I'm Matt Sergei (do call me Matt, please) and would like to help you -
please share your book URL first. It's crucial to analyze book page first and any links to it to tell what, how and when the optimization can be implemented.
With the above:
1. Can an Amazon book page be edited? If adding additional access to the the book author's page allows for editing a book page as well, you should be fine to do that or both (allowing access to profile, of course strictly professionally).
2. Do you or several authors (if there are more) have the book author's pages?
3. You do not object for any web promotion work that will be done for the book (e.g. all 100% legal to push book ranking and sales). Removing any web page/post (less than any on Amazon site, of course) that helps book sales is 100% in my hands.
The bid is for 300 sales divided to 6 milestones per 50 sales. They should be paid after every 50 sales achieved, if 300 is not achieved in 60 days the job can be cancelled (but not marked incomplete to harm me and not giving any rating/review because it's really non-deterministic e.g. those sales cannot be guaranteed). Or contacting Freelancer to adjust the job total amount that will cut my earnings (because Freelancer takes 10% provision from freelancers at start, milestones are adjusted).
So, do pass me more details first. Otherwise I'm a webmaster, developer and former technical writer for 26 years.
Regards and hope you're safe,
Matt