Q: Two cylinders are not working, car runs on 2 cylinders

Was driving and when I pressed on the gas it wasn't registering, then smoke shot out the back and I heard a grinding noise. Now the car only runs on two cylinders. The spark plugs were not hitting in the two cylinders that weren't working. I changed the spark plugs out, when I changed them one had alot of oil on it. So I also changed the head gaskets and the spark plugs. Still only two cylinders hit. When I go to start it, you have to hold the key turned until it catches, as if it has a bad battery and trying to get enough juice to turn. Sometimes have to give it some gas to start. I tried to drive it around the block and it runs on 2 cylinders as long as I keep pushing gas. If I let off, it will idle down and then cut off. If i start it and don't go anywhere and stay in the garage, it will idle but barley. But once I take off and drive a bit, it will not idle. Have to hold the gas down to keep it from shutting off. What could this be ?

My car has 65000 miles.
My car has an automatic transmission.