1
Listings in a child category are not included in the parent category, this is by design. There is an option to include listings in a child category on the archive page of the parent category, but this doesn’t extend to GD Elements.
I will ask the developers to take a look at your idea and whether they can consider enabling this through a snippet or option in the near future.
2
Making a parent required is a good idea, also, and sounds like it would be a solution. This is the way that it worked in V1. I will ask the developers to consider that, too.
For now, this isn’t how GeoDirectory works, though, and we do not provide customizations here in the forum. Both of these would require your own customization outside of what we can help with directly here in support.
Both of these could be accomplished by a GD Expert here:
http://geodirectoryexperts.com/