what do the deaths of key characters in the book (porky logan, malachai, edgar) illustrate about human nature?

Consider that all of these characters die because of their personal reactions to the disaster. It is human nature, both good and bad, that results in their demise. Take for example the character of porky.

Porky is a greedy man who dies from radiation poisoning. The irony is that he steals and hoards jewellery. It is the jewels that he loots which causes his poisoning and subsequent death.