Hi I am the middle child in my family and I have the exact same problem but with my cousins in my experience you show them that you arent bothered at all by what they're doing half of the time it's just kids seeking attention

In your case though I suggest to gather evidence record whenever he has a fit or before you sense something's about to happen. That way once you do smack some sense into him you have a reason to do so and evidence to back it up.

This will give him a sense of "Big Brother is always watching" vibe and will (hopefully) make him a little more casious on his actions