Hi,
1. You have the "product_manufacturer_id" column for that.
2. It's probably because you have variants. The hits are only for the main products but if you don't set a filter to display only products in your mass action, then you'll also get these variants listed. Also, in most cases variants don't have a name as it is generated dynamically based on the main product and the characteristic values.
3. There is no way to easily do that with the mass action system. The best you can do is to display the product_canonical column which, if filled in (which it should be for better SEO), will display the URL of the product on the frontend.