308 Armrest bolt

Definitely fastens with four points... Up front, if I recall, is a door stud sticking out with a fat washer and nut (in front of door lever); one position back, there's a stud with a black acorn nut (behind the door lever); then there are two bolts that go into the frame, philips head.

Total of four...

 

My 78 308 has two forward studs coming out of the door for the forward "grab area" of the armrest. The mid and rear portions of the armrest are secured by what I believe are M-5 size screws, phillips head. I replaced all of mine since I found a mix of hardware, sheet metal screws here and there. An unnamed dealer did this.
I had to run a tap through the nuts "welded nuts" in the door in order for the screws to work, the improper sheet metal screw inserted at some point in the car's life disturbed the threads.
I used stainless steel for all the hardware. Up front on the studs, I used SS fender washers and nylock SS nuts...then topped off the long studs to protect one's skin using SS acorn nuts.
With my Dremel tool I carefully reshaped the fiberglass where the aft armrest screws go through the armrest...This way when the screws are snug, they fit flat and squarely against the fiberglass of the armrest. Now the armrests are secure with nice hardware.