You would benefit from re-reading Chapter Eleven, which is when the author moves away from looking at the final few years of Chris's life and examines instead his background and his parents and his early years. One key aspect that created an obstacle in the communication between Chris and his parents was their feelings that wealth was something that should be enjoyed. Note the following comment about this:
Walt and Billie had both known poverty when they were young and after struggling to rise above it saw nothing wrong with enjoying the fruits of their labour... [Chris], the teenage Tolstoyan, beleived that wealth was shameful, corrupting, inherently evil...
We can understand therefore why it is that Chris was so "embarassed" by the wealth that his parents enjoyed. In addition, we can see how this created massive conflict between them when his parents offered to buy him a new car replacing his old one, which, according to Chris, had nothing wrong with it whatsoever. This was a key element that alienated him from his parents.