Is there an abrupt change in direction in this sentence? No, there is not, so the dash should be replaced with a comma.
Could parts of this sentence be written as two shorter sentences? Yes, they could. They wouldn’t flow the same way, but the new sentences would nevertheless be grammatically correct. Thus, this sentence (say it with me) needs a comma before the conjunction.
You should also use a comma after the conjunction here, because I swear to god is a parenthetical phrase (I know it’s a bit confusing that not all parenthetical phrases are enclosed in parentheses, but that’s the way it is) that needs to be set apart from the rest of the sentence regardless of whether the sentence is compound.
“Put down the burger, or, I swear to god, I’ll shoot you in the knee!”
(WordPress’ auto-correct is especially psycho today, de-capitalizing proper nouns, underlining entire paragraphs as incorrect, and generally making a nuisance of itself. *sigh*)