Never, ever type chapter/section numbers manually!
If you have read the
appendix documentation, you would know that
\appendixpage will create a “part-like” page. So, don’t use it.
Since you are using the standard class:
book, there aren’t many hooks we can use. So I proposed the following:
\suppresschapternumber makes the numbered chapter to be typeset as an unnumbered chapter, and it changes how the rest of the chapters are written into the ToC.
\removedotbetweenchapterandsection, well, removes the dot between the chapter letter and the section number.
Use the following with extreme caution!