I think you need to work on your story. How does someone:
- That's at a "dead stop" cut you off? Did he pull in front of you from a stop?
- "nearly cause a pile up"? Not saying what he did was right but...a "pile up".
- He's throwing stuff at your car while following you? Guy must have a good arm.
- How do you know he was coming to fight you? He could've been trying to get your attention to apologize.
- "test" their brakes during a potential road-rage incident?
I'm just sayin'. You really need to consider how to handle situations like this before they happen. I'm thinking it's a good thing you didn't have a gun, personally. And keep in mind had this incident escalated these are all questions you'd be having to answer. They're all questions I'd be asking you if I was the investigating officer. Apparently nothing came of this incident...but posting on an internet forum usually isn't the best course of action when you're talking about road rage and guns and such.