Hi,
You're talking about different things at the same time so I'm not sure what your problem is...hard to provide a fix in that case.
The line $this->setLayout('listing_'.$this->params->get('div_item_layout_type')); is to load an item box layout (a layout for a box of a product) while on your screenshot, you're showing the "type of layout" option of your listing module and that option is for the layout of the whole listing, not for each element of the listing.
Reading the end of your last message, it seems that you want to create a new type of layout and not a new item box layout.
So editing the item box layout files won't help.
Actually, there is no option to create new layouts of listings.
There are only these three layouts: div, table and list.
And you can customize each one.
I doubt that you're using all three layouts on your website. So simply edit one of these (listing_div, listing_table listing_list) that you don't use via the menu Display->Views and modify its code directly to suits your needs.
Regarding the blank page, you must have the error. If you don't see it on the page, then it means that your server is configured to not display the errors but log them. So you'll have to look in the PHP error log of your web server for the Fatal error message which generate the blank page. That will provide valuable information on what's going on and we'll be able to tell you what to do.