1. Fault in an accident can be spread across every party that was involved, and no matter how negligent one part was, that has no influence over how negligent every other party also potentially was.

2. A driver is typically responsible for being aware of all potential hazards on the road, not just the ones immediately ahead in the same lane. For instance a car that has started indicating to move into their lane from another lane (as this Tesla did ~7 seconds before the collision), and a car in their lane that is coming to a stop (this Tesla had completed the lane change pretty much 3 seconds before the collision).

Obviously the Tesla is really pushing the limits of what would be considered a safe gap, and coming to a stop in that location without a proper reason is obviously negligently dangerous. But the negligence of both parties contributed to this accident, regardless of who was most at fault.

You seem to have your terminology confused. Reaction time doesn’t even necessarily have anything to do with driving. I suggest a quick web search next time before assigning people remedial physics.

No, reaction time means the time from noticing the need to brake to the time brake pressue is getting applied.