Thanks for taking the time. Just to be clear, there aren't a lot of questions (I've been throwing out 'possible' questions to respond to after you weren't expanding on broad statements, hoping that you could use one to build on, like writing prompts you may give your students). I was honestly just asking you to embellish the points that you initiated.
There are two points I hear you making, and forgive me if I'm incorrect, but I think they're important to differentiate. The first is Tarantino's racism, his "problematic" nature, and his intentions with the film, which have been spun into conversations on how he assesses his own bias or not, subverts catharsis, etc. I've argued that he's painting a fantasy, but one that exists as a specific fantasy where we must be aware of our biases and history throughout. However, this fantasy takes place in a Western with two-dimensional villains. Stephen, your other point, is that core villain. I wouldn't base Tarantino's intentions off of when cheers erupted in a theatre, but yes I think that along with the white slaveowners, Stephen is supposed to be damned as a villain. He has gone out of his way to be the catalyst for Django and his wife's harm, and as Django's antagonist and the villain of the Western, his death will be cathartic. I don't believe that Stephen specifically gets the 'most' cheers though in his death (the sister's gun blast rocketing her into the other room got the most cheers in my viewing).
Singling him out as being a problematic character, rather than just allowing all those who contributed to oppressing slaves to be culprits, feels like a nervous white-savior position; inserting oneself into what "should" have happened because it makes one uncomfortable to see a black man in slave times be a villain, rather than taking (what I believe to be) Tarantino's position and skewering all who assault innocent black people, including other black people. It's a lot easier to point at the director as being problematic than unpacking our own issues with these choices and why we need more from them (like Waltz who just cannot sit with that discomfort and must make an attempt to separate himself from white people's inherent racism with a tangible, yet consequential, act). I also agree with you that Tarantino did have his cake and ate it too in Inglorious Basterds but explicitly said I don't think he does that here- until that very ending (which as I said before, I think is a sublimation of that inner conflict, coming out finally in on-brand exaggerated movie terms).