Please realize that there is a vast dichotomy between the way Native Americans are portrayed through Victor (the main character) and his family members on the reservation! This is the difference between a positive portrayal and a negative portrayal.
Let's explore the positive portrayal first: the one through the eyes of Victor. Remember, Victor, even though he is a child, is also a Native American! He is thoughtful and sensitive and incredibly introspective and smart. We can see all of these qualities from the very beginning in Victor's metaphor for violence: a storm (in fact, a hurricane). Victor thinks and thinks about the violence that erupts between members of his family and especially between his uncles, Adolf and Arnold. He also covets his books (a great sign of intelligence):
I used to sleep with my books in piles all over my bed and sometimes they were the only thing keeping me warm and always the only thing keeping me alive. Books are the best and worst defense.
In regards to the violence that he witnesses, Victor also sees the connection between that abrasiveness and the abrasiveness that has existed among his tribe through hundreds of years. Victor appreciates his mother's attempt to allow him to follow his dreams. He cries in worry about his parents' safety during a wild party. He cuddles them in love at the end of the story. Here is a young man who has the potential to "save" the tribe through all of his positive, Native American attributes.
Unfortunately, there is also a Native American stereotype perpetuated by Victor's family. It is a stereotype of violence, poverty, and alcoholism. Violence is exhibited by many (and especially by Adolf and Arnold). Poverty is evident by the socioeconomic status of everyone on the reservation, and even in Victor's mother's attempts to help him feel a full belly. Hunger is real for this family! Alcoholism is apparent in the wild parties his parents throw. In reality, it is alcoholism (as opposed to a tendency towards violence) that makes the family members hurt each other. It is also the reason why Victor's parents are passed out on the bed at the end of the story.
In conclusion, it's interesting to consider the purpose of this treatment of the Native American. In my opinion, some of the purpose is to show that the stereotypes are not totally unfounded; however, there are Native Americans (like Victor) who combat those stereotypes in the way that they live their lives in opposition to them.