Ford F150 problems-starts hard, gas problems

I have a 1994 F150. It has been dependable but gutless and poor on gas mileage. It has 108,000 miles. BOth gas tanks were empty so I filled them. THe truck then wouldn’t start at the gas station. I hit the front/back gas tank switch and it choked to a start. I drove it 140 miles fine, parked it, 20 minutes later it was very difficult to start. Next day it wouldn’t start again, but finally did. Next day I put a gas cleaner additive in, now the gas gauge doesn’t work, shows full on one tank that is 1/4 full; front tank had only about 2 gallons gas, I tried to fill it but it came spewing out. RUns okay right now, but what could the problem be with the gas? Any ideas? What should I look for first?

Have you checked/changed fuel filter(s)? You might want to have the pump(s) pressure and volume tested.