What can readers infer about the ethics and attitudes of the mormon faith from what the author shares about her mother and grandmother? why does the author want readers to understand the mormon culture?

Well, we can see in the writing that a lot of Mormon's ethic and cultures seems unconventional or even unreasonable for most people.
But, the followers do that because they believe that it's all important to purify their souls, and i think we all should respect everybody's beliefs

In 2081, everyone is equal not only in the eyes of the law but in every way; nobody is smarter, more athletic, better looking, etc. than anyone else. hazel is of average intelligence, which means she can't think about anything except in short bursts, and george has an intelligence way above normal.