Garage door sticks on a bolt

Carefully determine where the wheels of the bottom of your door stop being used. Any point below the bottom of the wheels when the door is completely down should be safe to remove. The track shouldn't have to go all the way to the ground.

I would not paint the track, for fear that it will interfere with smooth motion. If anything I'd use grease to lube up the track, which will put a protective surface on the inside of the track where you need it and improve performance (less resistance).

Rust on the outside of the track won't matter except aesthetically.

It sounds like the chain might not be on the sprocket that drives it. Get up on a ladder and look at the top of the unit. You should be able to easily see if the chain is off the sprocket. Try running the opener while you are up there too.

If the chain has come off you will need to loosen the chain tension, place the chain back over the sprocket and tighten it to the correct tension. Your user manual should have details on how to perform this but usually there is a screw you adjust on the trolley that controls the tension. Make sure to disconnect your door from the trolley before you do this.

Here's YouTube video that shows the process.