8GB Sandisc cards are actually quite easy to find. I got mine from a computer fair in central London, but there are many shops online (and even some electronic shops like Curries) that sell them. The hardest part in buying online though is finding an authentic one - there are far too many compressed fakes online.
Back to the question at hand... how can you quit a game on the M3 Real? I thought you just turn it on, run your game, and then turn it off whenever you like. The 'soft reset' function allows you to reset the system, but it also causes problems with some games. What exactly are you doing to your DS to make it stop working?
Also, why would you need to do such a drastic action like reformatting and reinstalling (re-copying) the Loader? No game affects the System files, and should not have any way of corrupting them either.