Welcome to the Forum!

For his 'limited advice' Ben hit the nail on the head!

For the rust, sand it down, clean the area and use Rustolium, or similar, spray paint to seal it.

If the cracks in the floor are bothersome or are deep enough to let the liner into them, you can patch them with a THIN coat of hydrolic cement.

I've got a LOT of experience with liner pools, feel free to 'pick my brain'