In "Notes," what happens to Bowker? What does he feel happened to him Vietnam? What does he ask O’Brien to do?

O'Brien starts the chapter titled "Notes" stating that "three years later [Norman] hanged himself in the locker room of a YMCA in his hometown in central Iowa," which finishes the story from the story just before, "Speaking of Courage."
Bowker wrote a letter to the narrator where he talked about how meaningless life now seemed after the war. He detailed how he couldn't keep a job for longer than two months, how he tried college but found it "too abstract, too distant, with nothing real or tangible at stake, certainly not the stakes of a war."
Bowker confesses to O'Brien that the day Kiowa died, a part of Bowker died, too. Seeing his friends and buddies die in horrific ways affected Bowker in a way that most people now attribute to PTSD (post-traumatic stress disorder). And O'Brien feels he must tell this story, especially because he did not experience the same as Bowker, but he (O'Brien) deals with his experiences by telling the troops' stories. And so he tells the story of Bowker, changing his name as Bowker asked.