Hi,
1. The simplest is to use a joomla streaming video plugin to include your videos into the description of your products. For example, this one:
extensions.joomla.org/extensions/multime...layers-a-gallery/812
2. What is a "files link page" ? You mean on the products listings ?
In that case, in the HikaShop options of the products listing menus/modules you can change the "item box layout" option to "Image and description".
Then, you need to edit the file "listing_img_desc" of the view "product" for your frontend template via the menu Display->Views and change the line:
echo preg_replace('#<hr *id="system-readmore" */>.*#is','',$this->row->product_description);
to:
echo JHTML::_('content.prepare',preg_replace('#<hr *id="system-readmore" */>#i','',$this->element->product_description));