ho does the interaction between Keller and Chris begin to reveal turmoil and struggle between the two?

I don't know if you mean to point us towards a specific interaction but in general, the distinction between Chris and his father Joe is that between a jaded idealist and a tragic pragmatist. Chris has returned from WWII jaded to find that the sacrifices he and America made (which include his own brother's life) have not seemed to change the world around them. However, he is still committed to an ideal of justice and believes there can be pure love and loyalty, which he shows through his interactions with his father and Ann, his brother's former fiance who he now pursues. Joe, on the other hand, is guilty of the negligence for which his partner (Ann's father) went to jail, a negligence that indirectly implicates him in his own son's death. Joe tries to temper Chris' passion for Ann somewhat, knowing it bothers his mother, but in truth Joe has to come to terms with a reality of denial due to his illegal negligence and refusal to own up to it. When Chris finds out the truth, he is broken not only because his idolized father has fallen, but also because with his father falls his idealism, his belief that justice can prevail and that the American way still has a purity to it. Let me know if you have specific questions about a particular exchange and I can relate this to that.