Make a subsite go directly to Access App, and App back to Home site

I am very new to Sharepoint (using 2013), so please bear with me if I use the wrong terms here:

My top-level site is going to break down into several subsites (3 for now) due to needing different permission levels for people depending on the site. What I would like is to have a subsite that is where an Access App lives (the app is already built and tested on a test site, just building the actual Sharepoint site it will live on for good now), and I would like it so that when someone clicks on the subsite, it will go directly to the Access App (no home page or landing page), and when exiting the Access App (clicking the "Back to Site" link at the top) I would like it to return to the top-level site.

I have discovered I can remove the link to the home page of the subsite in my list of links, and add a link that goes directly to the App, but I'm hoping there is some way to make the app and subsite behave differently all together, since I want that "Back to Site" link to go to the top-level.

I need the app on a subsite as we want only 3 or 4 people to be able to actually update the database, and everyone else just views it in-browser, however, everyone needs to be able to check out documents and work with a OneNote notebook as well, so the subsite is necessary.

If making it actually behave this way is impossible, could you suggest a good way to get people back to the top-level site when they go out of the database?

Thanks, ~Sydney