That’s correct this way. You can turn off the black background if you want in the field settings. I would also recommend to make that field required, so every review has to have linked entry being reviewed.
Showing the field makes sense for the listing view, since the rest of the review (title, images) doesn’t necessarily show WHAT is being reviewed.
Yes. Put a link somewhere. In the sub-menu, the sidebar, wherever. You can directly link to the form to create a new review record.
Sure, you can use categories. You can use anything that Pages can do. That’s the beauty of building this on top of Pages. 😉