History is used here to allude to his recalling of memories as his head is shot. The bullet goes through his head and while doing so, acts as the base for a timeline that opens all of his memories. This word also help to explain the time line since he is going through his memories from start to finish in the timeline. Moreover, memory is the analysis of a person's history.

This sentence alludes to José Olivarez' mother, specifically his childhood with his mother where he doesn't know anything yet. Therefor, everything is possible. Aside from that, This also helps with understanding the content of the topic in which the three people are discussing.

This is meant to say that he is the person that takes charge of his life and no one else. Also, by not using capital letters at the beginning of the sentence(s), it allows it to seem more intimate and less professional, scripted.