First of all, I edited your multiple questions into one because eNotes allows only one question at a time.
The intra-hatred theme in literature refers to a type of strong dislike between members of a supposedly tight-knit group such as race, gender or family. Song of Solomon contains several examples of this theme.
First, the novel deals primarily with poverty-level black Americans living in the North and in the South. The Dead family is an interesting example of intra-hatred. First of all, Malcolm Dead is wealthy and attempts to collect money from poorer black citizens. This creates a feeling of contempt and even fear of Dead in the poor black community.
His son, Milkman, has to straddle both of these worlds. He tries to fit in with his streetwise friends while also living in his father's world. His father subliminally sends Milkman the message that being black is somehow a curse and drives his family through wealthy, white neighborhoods in order to show them "a better life."
When Milkman's believes his aunt Pilate supposedly has gold, he sets off to the South to investigate a side of his family that he has never know. In doing so, his close friend Guitar believes him to have stolen the gold that Milkman had promised to share. Here, the previous examples of jealousy that Guitar, a poor black man, has simply been joking about turn very serious. He kills Milkman because of this hatred even though Milkman never had the gold.