HELP

HELP. My truck started backfiring today. Sounded like a gun fight was going on. It spit and sputtered til it shut off. I tried to re-crank it and it wouldn't let me. Ended up having to hold the gas peddle down, then tap and release it to keep the truck started. There were also "flames" in the throttle body. But I also noticed that a spark plug had a small burn mark near the spark plug wire connector piece. There is a foul gas smell that comes out every time it pops. When I change gears I have to hold the brake and the gas at the same time, slowly and barely let off the gas to switch the gear. Dies at a complete stop unless you are tapping the gas while holding the brake. The truck can not stay running unless you are slowly tapping the gas the whole time. I can not just hold the gas down and drive unless you want it to pop way more than it should. But 3 different times it has been drove today after this started you can not physically drive it more than a couple minutes without it popping a lot more and slowing down but the rpm is saying its in a different gear and it will just shut down. And it makes it harder to re-start. Unless there is a long waiting time in between. Now is there any body who can help me with this?