sound like you removed the repos by accident or intentionally, and for the media. Can you see them in File Manager? if you can then it meant that your tracker is either skip the folder (if you use tracker-cfg app), if it is not there then it meant that your eMmc is either formated when you tried to set permission and played with The commandline. Terminal command line for power user was never meant to play around with for a none linux savy.

By the look at your problems, it is seems you repartition the eMMC to do something that not the standard setting for it. Were you doing anything to it before it stopped working? Trace your steps and relocate your problems.
The best thing to do now is go into one of the electronc store and buy yourself a microUSB and relash it. It is the fastest way to fix your problem. The worst way is to trying to resolve the problem via commandline but that would end up taking longer than you can afford.

N900 will not go unstable without your own silliness faults, if you installed bad applications then you'll suffer from it. Extra-Devel is a dangerous place for beginner, even for me I find it scary at times.