Moz page grader is just a tool that makes recommendations on "best practices." You can ignore it's recommendations for things you think are fine for your users or not obvious red flags (missing title tag for example). I see no problem listing the full, official product names for each product. If that's what they are called, that's what they are called.
Also, I like when e-commerce sites show 20-30 products per page, as I find it showcases a good product mix and also isn't too much of a drag on overall site load time.
One thing I would strongly recommend if you have a bunch of nearly identical products is SKU grouping. People might search for "4 gig" or "8 gig" USBs, but perhaps they don't search for red, black, blue, etc. Consider putting all similar brand "4 gig" USBs on the same product page, then allow users to select the color. This could possibly have a major impact on the number of products in your product categories. I also think it's better for both the users and the search engines.