Hey Jean,
Look at the libraries\compojoom\layouts\galleria\galleria.php file - this is the layout that we use to render galleria.
In single view we do this:
$layout = new CompojoomLayoutFile('galleria.galleria');
So, you would need to load the js and css of your theme there.
videos are complicated & they are not supported right now. The problem is that to serve video well you need to have it converted into several formats etc. and then you need a fast server to serve those videos. So, right now they are not supported & I'm not sure that I'll ever offer video upload in hotspots. I'm more thinking on ways to offer youtube support.
Regards,
Daniel