I forgot one thing. You need to add the word "view" to your View's Custom CSS ID field to fix the formatting.
The reason for the 404 is because you have these products in a hidden category and when you try to get to the hidden category, it denies you access... because it's hidden.
But given your current set up, you don't actually have a Datafeedr product detail page so it really doesn't fit into your current set up anyway. My suggestion is to remove the link to the product details page or make the category unhidden...