why was malcolm's family better off than most blacks in east lansing

They built a small house and raised most of their own food.

"Better" is the operative word.  Malcolm's father was a strong-willed man with integrity as was his mother Louise.  If that makes for the Little family to have been deemed as having had a "better" life than most in Lansing, then so be it.  The family was harrassed because of Earl Little's nationalistic messages which were perceived as threatening to anti-Black groups such as the Black Legion and the KKK.  I think instead of the word "better", progressive, might be a more apporpriate term.  Malcolm's family had pride and a sense of who they were.  If that made them "better", know that it also made them "targeted".