Take a look at
this filmstrip. It covers some of how the door latch and lock works.
Also Walter has done some good work on latches, specifically adding a key lock to the driver's side latch. His thread is
HERE. That thread is in the works to become a tech tip. (John and Peggy - are you seeing this?)
Likely you'll need to remove the latch assembly and clean and lube it at a minimum.
Good luck. If you have more questions after reviewing the above info, please post them.
[on edit] the key won't turn much more than about the amount you're showing in your pictures.
If the door remote (inside handle) won't lock the latch, it may need to be adjusted toward the latch. The attaching bolt holes are slotted to allow in to move forward or backward.
