Well, if you jump start your battery with another car as the power source, it may not matter so much that the battery is "so dead". Besides, it's the alternator that charges your battery once the engine is running.
I'm not sure what your problem is, I'm no expert, however, if you have power, but are unable to start the engine, it would make sence then that it could be your starter.
Has anything gotten wet recently? What about fuses?