Apologies for the delay with this response, I was away on holiday, but we should have replied.
Re the 50% memory usage, you can slim down the amount of applications loaded during startup. See
https://droidboxforums.com/threads/startup-manager-free.86/ for some more information. HOWEVER, you may well find that you don't save many Mb of memory, even with a slimmed down startup. Bottom left of the homescreen there should be an icon you can click to force applications out of memory. Android's memory management does a pretty good job by itself, but some like to have manual control as well.
Realistically, you can't upgrade the RAM in these sort of devices, same as with smartphones/tablets. If you were handy with a soldering iron, can write Kernels and don't worry about your DroidBOX warranty, it might be theoretically possible to remove the old RAM chips, solder on larger capacity ones, but I think you'd then also need to rewrite the firmware a little for the new hardware configuration.
(not meaning to ignore your xinternalsd and WSM query, but haven't used either previously.
