You are way off, at least with your points about the language, I am not going to get in to issue of gun violence. You are viewing this whole movie from an outdated perspective. I don't mean to say that you are alone, or necessarily incorrect, but when Samuel L Jackson's character gets shot at the end that audience member next to you isn't "that's awesome" about the use of the N word. They are appreciating the way retribution is delivered to one of the most evil characters in the movie. They are commenting on how a simple line and act mean so much more, and relishing the justice that's delivered. That line is a clever turn on the expected empty gun/final struggle scene. The pronunciation is off, but it's to make him sound like a gangster on purpose, that is the only blaxsploitation that I saw, and its a conscious choice to appeal to a modern audience because while this movie is a western, it is so stylized and historically inaccurate that it cant be called a period piece or carry the expectations that go along with that title.
As our society continues to evolve, and we get further and further away from the despicable acts of that characterized a much less honorable America, the words of those times hold less and less weight. Tarantino's use of the N word is more a commentary on how commonplace it was in speech back then and its a reflection of the times and the ignorance of those characters. Jamie Fox's character is ignorant in his own way, having been surrounded by the horrors of slavery he doesnt flinch when something awful happens to a slave (the dog attack).
This movie constantly highlights the lack of intelligence of every single white character except the one who abhors slavery.I'm almost suprised there hasnt been a more vocal reaction from white supremacists upset at how they are portrayed. Both Jamie Fox (On NPR) andSamuel Jackson (interviewed by Jake Hamilton) have commented on the use of the word and I encourage you to listen to both of them.
I personally would be more offended by a that has slavery, racism, and graphic violence at its core but abstained from using the N word. That's like saying "It's totally okay to torture a black slave, but we will not use that filthy word". That doesn't make sense and continues to give that word more power then it has ever deserved.