1. You have actually found a bug I haven't know of. The checkboxes should be limited to a 200 pixel height and used with a scrollbar, but that's not happening.
I've applied a quick fix, by adding extra custom CSS code. Now if you choose the “checkboxes” option, it should display as a 200 pixel high element, with a scrollbar, not overflooding the page.
2. There was an error in your configuration
2a. You had the Brands and the Tags selected to return as results on the General options -> Sources 2 page, thus the plugin was returning these items as well. If you remove them from the list, it's going to work as expected.
2b. same as the 2a.
3. That is unfortunately not possible yet. I'm currently working on the next update, and this is one of the features I have to solve yet. I'm planning to add an option to allow displaying either the latest matching results, or results to a search phrase. I believe that is what you are looking for.
4. Same as 3. There is no date filter yet available, but it's coming with the next update. I was already working on it for this version, but it turned out to be a really really complicated issue. (basically working out a solution that does not affect the overall search performance is the problem)Best,
If you like my products, don't forget to rate them on codecanyon :)