Help with idling issues

I have an 89 tercel wagon, manual, carburator, about 125,000 miles on it. The problem I'm running into is that it likes to stick at above normal RPM (1500 - 2000) sometimes. It settles down to 750 RPM when I stomp on the gas and rev it real quick but that only lasts until I give it gas to go. The gas mileage is decreasing a little also. The car also won't idle on it's own whether in gear or not. If I want to warm it up I have to sit in it because if I let off the gas at all it dies, but that is only until it warms up... and idle at a stop light after driving is usually fine.
Also when I shut off the vehicle it tends to sputter and "choke out" like it is still getting some gas. It then lurches (like stalling in first gear when trying to go from a stop and not giving enough gas) if I let the clutch out while it is sputtering. The last little relvent bit I can think of is that after driving it, the car smells strongly of gas... there is no visible leak that I can see and there hasn't been any gas on the ground afterward but it smells very strongly like unused gas.

Any and all help is appreciated

Thanks