I worked a little more on my odt file, adding structure (title 1 and 2). My title 2 insert automatically a page break. I also added a TOC and one image.
The image was correctly processed, though set just a little on the right, maybe because of the small left margin on your CSS (not sure of it).
The text is very well processed but the created epub is lacking an hypertext TOC. I think this a an important requirement you should address. I have seen this feature implemented very cleanly in Sigil, in a little more confusing way in Calibre. If the original odt text has a structure (as many have), then the epub created out of it should have an hypertext TOC mirroring this structure.
It seems to me the way to go is to let the user chose on your extension which title to hypertext (the "Sigil" way). Up to now if we want to use this feature we have to use calibre or Sigil.
On the other hand, the dedicated TOC created in OpenOffice.org odt seems to be useless because it only duplicates awkwardly the epub hypertext.
Last thing. It seems that a one page Preferences panel, grouping metadata, splitting, fonts and TOC would be simpler. This way your extension would have only two buttons:
- Preferences panel
- Processing button