Ah okay, so what would you suggest I'd do? I don't have another device, so my only option is to upgrade this one to 10.6, but I guess I won't be able to use gateway anymore then?
Above all things: DO NOT UPDATE YOUR DEVICE TO 10.6! So, with that said: I suggest buying a regular flashcard (one that plays Ds roms on your 3ds, not sky3ds ect) and using that to install CFW (rxtools for o3ds, reinand for n3ds). Or just buy a gateway flashcard. I think you don't need the browser in order to get gateway to work.
Is there absolutely no one near you with a 3ds?