There is a police officer at the police station, far more often than not, or quite nearby.
Unless the other driver is physically ramming your car, you are not being harmed one whit.
Dial 911 and report an aggressive drunk driver.
You have absolutely no legal cause to even display a firearm until your disabled car is approached by the other driver with obvious intent to pull you out and beat you or some such thing. Until then, you can drive away, or get out and run to an area a car cannot go.
Why would you engage in automotive 'mutual combat' with another driver and potentially escalate the situation into a manslaughter charge against you? Just drive off and be done with it or find a safe place and park while you call the police.