In most cases, getting out of your truck is the wrong answer, tactically & legally.
One, you are leaving your "domain" and entering a public space - it can make you look like the aggressor.
Two, you can have your weapon to hand and out of sight inside your truck. Outside, that would be brandishing.
Three, his truck is a weapon and yours is your armor. Don't get squished.
Great points. To build on this a bit:
1. Park so you can leave quickly if necessary. You want to limit his ability to box you in and you don't want to back up if you need to leave. Make sure you have good visibility in multiple directions.
2. Get a higher end dashcam and learn to use it (they're available for under $300). If you park properly, you should be in position to record what he's doing. If a confrontation does occur, make sure you're either inside your vehicle or within the visibility of the dashcam as much as possible. My guess is that a dashcam is both more convenient, easier to use, less likely to have battery problems, and will appear less threatening than recording with your cell phone.
3. You can always try and make nice by sending him anonymous gifts