The lyrics, melody and chorus are obvious references to The Rolling Stones “You Can’t Always Get What You Want.”
Moreover, “kingdom” and “watch” are obvious wordplay choices referencing his collaborative work with Jay-Z, Watch the Throne.
Both Kanye and Nas deliver simple, sentence-long bars, wherein they deliver one or two rhyming syllables at the end of those bars.
Django Unchained is a Spaghetti Western owing much of its inspiration from Sergio Corbucci’s 1966 film Django. Similar to Franco Nero’s Djano, multiple motives compete for primacy in Jamie Foxx’s character. Namely, revenge against his former slave owners and love for his slave wife, Brunhilde. The latter inspires him to embark on a quest to rescue Brunhilde from a dubious and villainous slave owner, Calvin Candie.
I think this is also clever wordplay and a cruel euphemism referencing black slaves. “Rats” are an inhuman and condescending reference to black slaves. In this line, a white slave owner is ordering that black slaves must be kept outside in the slave quarters and out of the house.
You are right to say that in this line CuDi is hoping that he will have the courage to live until thirty years-old, however, I do not think this is a social comment regarding the average life span of black Americans. That he “hopes” to “see 30” states his uncertainty clearly. Given the overarching themes of the song, his “hope” implies his fears of suicide.
The line “in the middle of the night, killers coming for you life” should be taken together. This is a reference to the “midnight walks” slavers would take with slaves.
He is right to say that the perspective of this song is that of Django. Given the nature of the perspective, Django (Ross) is questioning the severity of punishment that a slave owner is doling out. It is not unreasonable to think that this is referencing the scene wherein the Brittle brothers punish Little Jody for breaking eggs by whipping her. In addition, this could also reference the scene where Django begs for the Brittle brothers to punish him in place of his wife.
Given that the perspective of this song is from that of Django, I think this is likely clever wordplay. Obviously, Django (Ross) is a freeman for all but the prologue of the movie. However, I do not think that this line examines only the physical chains of slavery. Despite his status as a freeman, I think he is examining both the psychological scars of slavery as well as the stigma of being a free black man in 1850’s America. As the narrator discusses later, the psychological scars inflict pain in his psyche long after he frees himself from bondage. Although Django broke free from his physical bondage, moreover, his status as a free man does not release him from his color in a racially divided America. Therefore, only the “realest” chains against freedom remain: 1850’s racism.