Parallel - "Perhaps he'd turn into a god and they to trees."
Its a parallel to God and the Garden of Eden in the bible.
Contrast - pg. 171 "There's not any people. What are you talking about?"
Its a contrast to what he has been telling his son. To him, there isn't anyone anymore, in the lawless hell that he and his son must survive in, but he keeps telling his son that they are the good guys.
1. Has his son gained some power now in their relationship? From 162 to 163 he starts conversations with the father and even orders him around a bit, something the father would do in his stead.
2. Is the old man's name a reference to the biblical character, Elijah?