The VM Product Module backend is not effective on our Product Module Carousel. We have used a completely different idea to list products in a row. Because in terms of "responsiveness" we had to do it. The "products per row" is calculated automatically.
Actually the "products per row" depends on 3 things:
1- The width of the module (the screen resolution of the device: desktop, tablet or mobile)
2- The "max-product per row" (by default it is set to 5 -- to avoid broken layouts)
3- The width of the thumbnails
If you alter the 3rd option (Width of thumbnails) you will get what you are looking for.
To do it;
1- Open the custom.css file (or any CSS file that gets loaded on your website)
2- insert this CSS rule:
.FlexibleFeatured ul li img { max-width:150px;}
(change the number of 150px until you get 4 products per row)
regards.