How should exactly the brake cable be fixed to V-brake caliper? Regarding the V-brake calipers, where the cable is tightened with a screw:
Should the cable go between the head of the screw and the washer (1), or should it go between the screw head and the body of the brake caliper (2)? And most importantly, why? (Is either of the two dangerous, e.g. could the cable slip or break?)
(1) Cable between the head of the screw and the washer:

(2) Cable between the head of the screw and the body of the brake:
Picture 2 is correct. The washer should prevent the cable being damaged or pulled by tightening the bolt.
However, on some cheaper brakes the bolt and washer are such poor quality that they turn together and the benefit is lost.
I will add that your cable in picture 2 isn't seated deeply enough behind the washer.

Note that i usually leave more cable and tuck it away behind the spring. This photo is OK for reference to clamping though.