My car won't stay running

ok,up to yesterday, my wife’s car started and ran fine. but we had not driven it in about 3weeks, and it was on empty. well, my kids would listen to the radio and, i think, starting it while we were at work. anyway, they ran it out of gas. so put gas in it, 3gallons, turned the key on and off a couple of times to get a good prime. started it up, died, i figured not enough fuel, yet tried again. started, but started spitting and sputtering and idling really ruff, had to hold to the floor to keep it running. removed the maf. it started and did the same. finally, i held down the gas and brake at the same time, took off to the store, got gas, but it died half way there. got it to the pump, put more gas thinking that’s the problem. nope, the same. got it home, but when i let off the gas, it idles like it’s not getting fuel and dies. so, any clue what it is? remember, 3 weeks ago it ran fine.

You ran it to the bottom of the tank. It may have clogged the fuel filter or killed the fuel pump. The fuel pump is lubricated by the gas in the tank.