Crank sensor

Hello,
My car broke down on the IA. It stopped accelerating on the highway. It would not respond to the gas pedal properly. I was driving seventy five miles/hour and all of a sudden it would not go past sixty mph. The check engine light came on and I pulled off. The mechanic fixed the car by changing the fuel pump (he also had changed the ignition coil, spark plug and fuel filter because everything looked so bad and he thought they were to blame first). After this the car was driving better than it had been prior to breaking down. It accelerated and drove in general more smoothly.
three hundred miles later, on an extremely hot day, when I pulled off the IA the brakes suddenly stopped working and the steering wheel seized. The car barely made it into a gas station rolling. The car then was having trouble starting. It sounded like the battery was drained when you tried to start it. It turns out it needed a new crank sensor.
The dealership, who sold me a car that has now broken down three times in under eight hundred miles of owning it is claiming that it was the crank sensor all along without ever having asked about the symptoms of the car prior to the original breakdown.
I am not very car-literate but I know what I experienced and how well the car functioned following the first mechanics assessment. He charged me only for parts because he felt bad it took him a couple theories to figure it out but he said the car was in such bad condition (things were plugged, disconnecting, leaking etc) that he was not sure where to start. He was upset a car in its condition would be sold. He also kindly gave me a list of four other things to get fixed in the near future for its safety and how much I should expect a mechanic to charge me for it.
I just want to know, do you believe the first mechanic made an error and it was the crank sensor all along or does it sound like two completely separate events?