Welcome to the VW ownership adventure.
I can't even begin to suggest why the motor won't start but remember the first rule; gas+air+compression+spark=fire. If you are missing one it won't work.
as for parts, start phoning around to wrecking yards in your reigon, you never know.
The door is probably falling out because the track on the rocker panel is rotted away. You'll need to weld in a replacement piece (big job) or lay a piece of new metal over the missing parts of the bottom track (mickey mouse but the door stays in and kinda rolls)
Good luck.