First off, I'm glad you are OK, but as a fellow gun enthusiast I'm extremely disappointed that you were reckless enough to fire a warning shot into the air. You should know that you NEVER do that. You'd be better off doing like Wytstang said and putting that warning shot into the ground between their legs, although I'm not a fan of warning shots at all.
In my opinion, you should have never let those guys approach your car. The second the guy made a move to get out of his truck, you should have been out of the car aiming for his center mass. If he kept coming, place one of those 10mm rounds dead in his chest. Just make sure you don't let anyone get behind you.
Don't mean to sound harsh with you, I know the adrenaline was pumping and you didn't have time to think about it, but when you are carrying a firearm you need to plan for these situations and know how to deal with them. Just learn from this ordeal and try not to make the same mistakes again.