I've only ever been on one side of this equation, so I'm exceptionally ill-qualified to proffer advice. But I think you're taking the developments in great stride. Knowing how hard I pushed boundaries, I bet I'll be blessed with quadruplets living the terrible twos until their twenties.
If it makes you feel any better, there was a time (incidentally, at the exact same age as your son) where I was obsessed with the n-word. It's not that I lacked the brain development to understand the reasons why it was off limits. I simply lacked the executive control to stop myself from relishing the thrill of dabbling in taboos. It wore off quickly. It's a stupid phase, but part of being sixteen is doing things you aren't supposed to because you aren't supposed to.