BSOD analysis can be very straightforward, or it can be very complicated. And, we don't know which it'll be until we start looking at the reports and getting some feedback.
Do the best that you can with my suggestions (and let us know of anything that you can't do).
The simple cases are usually clear cut and have a definite problem that stands out during the analysis.
The complicated cases are usually a pain to fix, and require a lot of work just to coax results from the analysis.
I don't research the ability of your system to add RAM because:
1) I may not have the EXACT proper system make and model
2) I do not know your financial situation.
As such, I leave that research/decision up to you - whether it be a PC or a tablet.
My suggestions are based on my research over the years (I started this about 10 years ago).
Obviously most of the research involved PC's and not tablets.
But, most of the suggestions still hold.
It would be easier if I just suggested that you wipe the system and start over.
That's what most tablet manufacturer's/repair technicians do.
I give suggestions that attempt to fix the system before resorting to that drastic step.
If my suggestions don't work, I always have more (until the last suggestion of throwing it out of the window :0)
USB devices are mostly used by plugging into a USB port on the side of the system.
BUT, there are quite a few USB devices (touchpads, card readers, webcams, fingerprint readers, etc) that are internal devices and use the USB interface.
The missing memory dumps can be due to several reasons.
The way to check is to see if they're there after the next crash - BEFORE using the cleaners
But don't be surprised if there isn't one - as the lack of RAM can cause the system to not save them.
Also, the lack of a pagefile (or one that's too small) can also prevent capturing one.
I'd suggest that you try to read the BSOD when it happens and let us know what it says.
BIOS updates weren't as big a concern with W7 and earlier. But with W8/8.1/10, the system communicates with the BIOS/UEFI much more than previously.
Also, errors due to the BIOS/UEFI being outdated are difficult to troubleshoot - as they tend to resemble hardware errors (and we go crazy trying to find hardware problems where none actually exist).
Quite frankly, I don't expect that 8% free space will cause BSOD's.
But I do suspect that low free space will cause BSOD's (as I've seen it happen in the past).
But Windows systems are constantly changing, so the exact number is different for each system.
My suggestions are a compilation of my experience over the years.
While I may mention what I suspect is the cause, my efforts are more focused on fixing all of the different things that I've seen contribute to crashes over the years.
In most cases we're able to fix things, but in some there's a need to reinstall the system and start over fresh.
When you uninstalled the unknown device - did it return after a reboot?
Have you checked to make sure that Windows Update hasn't turned itself off?