The gas gauge hasn't worked accurately for a.

The gas gauge hasn't worked accurately for a couple years. We would put gas in when the "checkgauges" light would come on cause that was a tell tell sign. Recently that method stopped working and we ran out of gas a few times (kept a gallon can in trunk) yesterday after traveling about 150 miles it ran outta gas again but would not start after putting the gallon of gas in. If you held the pedal down it would sputter, start n die. We let it sit for an hour or two then it started fine, even idled. Today when we went to take it for a short drive it did same thing. After sitting awhile it started fine but after driving several blocks it sputtered ndied. Now it won't start, tries to but just very rough/missing sounding and smells weird almost like sulfer. Not sure ifthis is a sign of fuel components or cat. Convertor. Any advice is much appreciated