In order to get an .epub book is better than to convert from mobi to epub with Calibre, to use Sigil to built your epub from the .xhtml/.html files.
And your problem with your title page is because the way you are using the cover image. I attach a new epub this time made with Sigil.
Here you can see how the title page appears now in Calibre:
and here how the title page is showed in ADE:
In the epub below you can see how I have included the title page image. But remember, use Sigil to build your epub.
Regards
Rubén