The reason you get places like ALL, is because your users or you are not waiting for the Google API to do its work, and are saving the listing before the API has assigned the correct location.
That can only be prevented by telling your users to slow down, and/or have a regular look at your locations and clean up.
The easiest way to review that occasionally is to look at your switcher, and if ALL appears there, you need to clean up, see image.
Review this BEFORE you clean up, or you will loose listings.
I explained already to you that the reason you get -1 to your slugs is because that you already had a lot of location slugs in your system from the previous directory plugin you used, and therefore you either needed to accept -1 in your new locations, or clean up all leftovers of the old system. You chose to not have -1 in new locations, so you need to accept what that means for your setup.
I have already offered to help you with this, and which I have explained that you need to do this as soon you notice a duplicate location slug (slug and slug-1) to minimize future problems.