it could be of running it with out oil.
It is possible it is one of the speed sensors.
One posibility to check would be the timing belt. If it broke while driving your car will stall and will not start again. If it was the timing belt you may have a more costly repair bill then just the belt.
Sounds like the fuel filter is plugged. when did you change it last?
depends on what car and what engine, typically if your cruising on a freeway, you will be running at half RPM or at the most 3/4, but the lower RPM the better with that you get better gas mileage.
On the open road or freeway with mild inclines.
I had this happen to me once. It was a bad alternator.
check your coil
Running out of gas, timing chain breaks.
Is the engine running ? no