Before spending all that money buying parts, try jumping your starter solenoid to start the car. There is a thick red cable or that runs to the starter that is always hot. There most likely a green wire with a terminal connector connected to the starter solenoid - this wire triggers the solenoid when you turn the ignition. You can use a screw driver with a plastic handle and make contact between the starter solenoid terminal (after removing the green wire that triggers it) and the hot red cable...make sure you have the ignition turned to the start position... this will jump your starter.

The cutting off occassionaly is could be a dirty throttle position sensor - preventing the car from idling at a stop.