Why is my SD card not being fully recognised?
The immediate red-flag is that you are using a Samsung EVO SD card. There have been a huge amount of counterfeits being reported, even from retailers like Best Buy and Target. It even made it on XDA, which explains pretty thoroughly what to look for: Fake Samsung EVO 64GB SD card - XDA

It doesn't seem, however, that it would affect your Settings app in that manner. I have a few unbranded tablets that handle storage terribly, and I think it's definitely the manufacturer's fault.

If you like Vanilla Android tablets like I do, I would recommend the Dell Venue line of tablets, they are Intel core and handle games and Bochs emulator very well.