Glad you're OK and didn't dump it on the highway.
2 major mistakes IMO:
Not enough lead time for highway speeds. If I can't get 4 car lengths minimum between me and the car in front, I pass or slow down to allow more space. Space is golden. There is no such thing
as too much space on the highway. I commute every day. I treat every car/truck/Jazzy chair within 50 yards of me as a potential threat.
You spent too much time trying to evaluate the intentions of the driver. With the distance you allowed yourself at highway speed the only thing you can afford is a very quick glance.
Something happened, he reacted to what was going on in front of him. You saw his reaction, and reacted yourself. About double-triple the normal human reaction time for an average oh shit!! incident-decision-reaction.
Jersey is notoriously full of ignorant, aggressive, oblivious drivers. I'm sure you know that by now. When I see Jersey tags up in my area, I steer clear.
Bottom line is you didn't allow enough lead room for the car in front. Find the clearest lane you can ride in in NJ, no matter what the speed and ride that.
My first near-major accident on a bike occurred in California on misty-wet roads from coastal fog in a near exact same situation.
I was following too closely (about the same as you) in morning heavy slab traffic headed for the VAFB main gate.
Christmas tree string of brakelights, diving front ends, I hit both brakes and went into a dead-lock straight slide headed for the car in front. As a low-miles novice streetrider at the time I was lucky to know enough
to quickly clutch it, release the brakes, get the wheels rolling again and I swerved it around the car I was destined to hit and accidentally lane-split it between the 2 rows of tight traffic, and not shitting my pants at the same time. I was VERY lucky to say the least.
Take care in Jersey.
Your post is pretty much a contradiction.
You state she should have allowed 4 car lengths (a distance you arbitrarily made up) while acknowledging how aggressive NJ drivers are. Commuting is not riding. Completely different animal. You leave 4 car lengths and you will constantly have cars taking away your space in the lane. You NEVER leave that much room, it's just too dangerous.