I have to be honest. I know that the Content Selection feature is part of the LTI Specification, but I have never found it very useful.
For the content selector to work well, you have to make a connection to a book, and then from the content selector, you can choose the chapters and parts that you want to select. What this means, to my understanding, is that every book would need to be set up as a separate LTI tool with the format https://site/book/format/lti
Most LMS admins I know, would much rather create the connection to the Network of books, not to individual books. I find it more convenient to export the entire book from Pressbooks as a 1.1 book, and then from the Moodle import page select the chapters that I want displayed.
While I can’t help you with the content selector tool, I would be very happy to help you troubleshoot the 1.1 connection.