There are several issues with your code.
Your document starts with
\backmatter
?
You are using package ledmac which is eprecated and should be substituted with package reledmac. If ou don't want to change, the error message gives you a clue.
You are not using
\chapter
, which is the essential structuring command in the book class. Only chapters will update the left header (default).
You are placing
\section
-commands in a center environment. If you want to change the appearance of section and others, you can use package titlesec.
You have pagebreaks and
\newpage
everywhere, indicating that you indeed want to have chapters.
You have several
titlepages
in the mainmatter. A titlepage is part of the frontmatter.
Two titlepages after another will cause the page numbering to collapse, as you already noticed in
two title pages in the book without restarting the pagenumbering.
Why do you have a section-command on a title page?
The smart way: Calm down and take a deep breath, read posts and provided links attentively, try to understand and ask if necessary.