I've never had screws fall out of a laptop that has never been opened. I suspect yours has been opened and the screws were over tightened when it was re-assembled.
To keep the screws in place, I'd try applying some thread-locker to the screws before putting them back in, and I'd get a bag of new screws to keep on hand. Take an old screw into a computer store or a hardware store, and match it.
Regarding your storage issues, I'm working on that too. I also have an R3-131T, but I've only had it for a few days.
You say an SD card didn't work. What happened exactly? Did Windows recognize the card in File Explorer?