The first is simple. The cover.jpg is not used in any xhtml file. You should have a xhtml file with the cover.jpg in it. That is also usually the first file in the ePUB. A lot of readers will not show the cover if it is not in a xhtml file.
The second, make the author heading 1 and the title heading 2. Rebuild your TOC accordingly.
You can have multiple authors in your opf. Use the following in your opf.
Code:
<dc:creator opf:role="aut">author1 & author2 & author2</dc:creator>