Hi mmurch,
I can help you here, no problem.
While you can’t configure the directory to switch the search page for the primary page of the directory, what you CAN do is use a shortcode (documented here: https://businessdirectoryplugin.com/support-forum/faq/valid-bd-shortcodes-2-1/ ) to pop up the search page on any page of your site. That way you can have users start there on a homepage, for example.
As for hiding the categories, we have a setting that allows you to show the categories, or the categories and listings (“Show listings under categories on main page?” under the Listings tab), but we don’t have one for just the listings.
You could use some custom CSS to hide that section above the listing if you want (using “display:none” without the quotes). Here is an article about how to use custom CSS with Business Directory in a way that doesn’t get overwritten on upgrade of BD: https://businessdirectoryplugin.com/support-forum/faq/how-to-use-custom-styles-with-bd-2-1/
That’s the best workaround I can offer there for now.