Question 1
Two factors that might explain why North Koreans have such a short life expancy could be the following. On the first hand, malnutrition derived from the food shortage that exists in the country, as its autocratic economic system cannot produce enough for everybody. On the second hand, due to the same reason, not everybody can have access to proper healthcare services as these are supposed to be public but do not have capacity or funding to serve the whole population.
Question 2
The satellite nighttime photo is attached. In North Korea we can see almost no electric lights, there is only a small spot located in Pyongyang, the countrys' capital city. On the other hand, South Korea is full of lights everywhere.
Question 3
The difference is due to the enormous difference in the level of development of the two countries. While South Korea is an important economic powers in the current world, which has experienced an enormous growth in the last decades and has specialized in high technology sectors, North Korea is an autocratic country governed by a dictator, where people still die for starvation and malnutrition.