For removing the page numbers, try the following which I tested in Sigil:
Code:
<span aria-labelledby="pg.*?" epub:type="pagebreak" id="page_.*?" role="doc-pagebreak"></span><span hidden="hidden" id="pg.*?">.*?</span>
I used '.*?' to catch the non-numeric page numbers since my original '\d+' only caught the numeric pages. (pgii for instance).
Please note that running this will cause issues for the index since those page numbers are used there.
Also note that if I send the ebook as a kepub, I don't see the blank lines.