The safety spring retaining screw could either be staked or it's just frozen. Try a little penetrating oil and/or some light tapping with a non-marring drift. Could well be just hardened oil deposits.
As for the rear sight, the only thing that comes to mind is that the coil spring is weak. Even this gunked up thing locks in place well. :
ETA: Missed Monk's new photos in Post #11. Hmmmm...