UPDATE to my previous UPDATE:
I figured out why GaiaGPS wouldn't allow me to save data (downloaded maps, etc.) on my microSD card instead of internal memory. I was attempting to tell it to move the data to the SD card through Samsungs "Device Care - Storage" facility in the "Settings", in which you can [supposedly] define/redefine the target storage location for each application. Even though I had designated the SD location, and even though it *said* that it was storing in the SD location, it actually was not.
THEN I found, while perusing the setup options in the GaiaGPS app itself, an option to designate the "Root Folder" under the "Storage" heading (yeah, I should have seen that before now). Viola! This allowed me to truly designate the SD location and, once done, the application immediately moved all my maps from internal to SD, thus freeing up about 16gb of space from my internal storage - fully half of my 32gb available. Suddenly, I've got plenty of room to stretch out. So, I won't be needing to find a new tablet after all - at least not in the near future. Life is good!
Steve