well, it seems like you're trying to create/validate an epub3 in sigil, which only supports epub2 right now.
for example, this error
Code:
ERROR: /OEBPS/Text/Section0002.xhtml: This file should declare in opf the property: svg
is being generated because the epub3 spec states that you need to attach a properties attribute to references to elements that contain scripts and svg, for example. in the manifest it would look like:
Code:
<item href="../Text/page.xhtml" id="page1" properties="svg"/>
other errors seem also epub3 specific, like the requirement for a 'nav' in the manifest.
you should check out the
epub3 specs for more info, or think about changing the file to an epub2 for better reader support