Moved to high altitude now my car won't start

1985 Ford Tempo. I just replaced the idle accelerator and my mechanic had me put in the gas some Lukas additive. I moved to a high altitude and drove the car there ok. I drove the car all day the next day. Then I took the car out and it sputtered a bit and died. Got towed home and I put in a gallon of premium gas. The car started the next day so we thought it was maybe the additive and altitude. I drove the car again to several places and then came out to leave and the car would not turn over. The battery is new and it tried to turn but would not start. I also put in 2 more gallons of premium gas and that did nothing. I had to have the car towed home again. Once the tow driver had the car at my driveway, he tried to start the car and it started immediately. He said then it is my fuel pump as towing it shakes it around and that is then why it started after being towed both times. I am on limited funds just having replaced the water pump and idle accelorator and a thermostat, had an oil change, a fuel filter change and a new air filter.

I know this is an older car but I just spent $400 on fixing things and now it is something else? Can you help with a diagnose? I don't want to keep fixing things and then it still won't run. Someone also says it's the spark plugs. How can I tell without sticking a bunch more money into this ole car?

Thanks