Brake Sensor problems of the 2004 Nissan Sentra

I was driving east on i494 near a major interchange, in very heavy traffic. I was in the center lane going approximately 60-65 mph when my engine suddenly quit. I quickly checked the lane on my right and it was clear so I moved over and onto the shoulder. My brakes and steering were going quickly, but I was able to bring the car to a full stop next to the guard rail. I was right next to a two-lane exit to i35, where the traffic was flying past me; several cars almost ran into me, with one extremely distracted driver crossing the line onto the shoulder and heading right at me. If he had not looked up in time I doubt I would be here to report this. I was able to get a tow truck, but traffic was not even slowing or yielding for the tow truck driver. It was an extremely dangerous situation. While waiting for a tow, I was able to restart my car after about 10 minutes, but was too afraid to try driving it in those traffic conditions. The repair shop I went to diagnosed a faulty O2 sensor caused by a leaky flex pipe and wanted over $800 to replace the pipe w/ catalytic converter, gaskets, O2 sensor. And spark plugs. Since my car would start but I did not trust it, I decided to drive home (25 miles) by city streets and back roads. On the way the engine again failed while waiting for a light to change. After 10 minutes it started and I was able to get home. I took it to my mechanic, who fixed the flex pipe. A few days later the engine died again and restarted after another harrowing wait on the side of the road. This time the car gave a code for the crankshaft sensor, which my mechanic replaced. Since then my car has not quit while driving, but does hesitate and I am afraid while driving it. I may have my mechanic replace the camshaft sensor as well, since that is also a known issue. I am supposed to move to California, but don't trust my car to make the trip safely.