I've read a lot but not all of this. Sounds to me like it was well handled but to the OP:
Would it not have made sense to call 911 as soon as the guys erratic behavior became apparent?
I have done that on a couple of occasions in the past - in both of them only to find out that I wasn't the first call about the guy in question. He'd been menacing drivers up the road for a while.
"When the Going gets Weird the Weird Turn Pro"
Hunter S. Thompson