Hi,
1. You can access to the view in the HikaShop backend. Under: "Display > Views".
Please edit the view for your current front-end template, otherwise the modification won't be visible.
The interesting block for you starts with
}elseif($this->row->product_quantity>0){
It requires some development and PHP knowledge to modify the code in order to have your wanted result.
2. At this moment I think that the "mass-action" feature could help your for this repetitive task.
You can take a look and make tests in our demo website.
You can also check the mass-action documentation :
www.hikashop.com/support/documentation/167-massaction-form.html
3. I know that you were waiting for an answer but we answer to all questions and we have a moderation system. So each time you make a reply to your thread, you loose your place in the queue and you might wait longer.
Regards,