Had the same issues and many more with the ignition. Had new copies of the key made from an unused spare kept in the sock drawer. Ignition began working like new again. (actually the first copies I had made were defective and after a week, took them back with the receipt to have them redone)
Didn't need to cut the wires for the seatbelt. (not to mention you can short the system while cutting them) Looking down in the lower pillar next to the motor is the wire harness. SImply unplug it. You may be able to find suitable replacements in the junkyard provided they haven't already been cannibalized.
The door jam switches often fail due to corrossion build up on the contacts for the door switch. But they never fail closed circuit, only fail open circuit meaning the dome light and door chime won't activate. (seatbelt however will) A permanent repair simply involves grinding off the corrossion with a hand file then applying silver-bearing solder (Radio Shack) to the exposed areas; being careful not to melt the plastics. Since the solder doesn't corrode very easily then a lifetime should pass before it reoccurs again. If you slap it back together without the solder then it'll be a matter of weeks before the corrosion causes the problem to reoccur again. | 
