Don't rip off that front air-dam off, its $300. Been there / did that on a DTS. You can't trim it up either. Its needed for cooling of the radiator. Forces air up & into the rad. Sorry. No modifications.

I have seen guys put a pc of treated 2 X 8 near the curb / driveway for smoother lift & over.

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Cadillacs are kind of "Low riders" as they come from the factory. Sounds like your driveway is better suited to a 4x4 truck. There's really not much you can do except to just keep pulling in at an angle.

is air ride working? did you lower car ? have wrong size tires ?. should not bottom if is a normal stock car

The only way to pull the car into the driveway with no scrapping is at an angle. Is there a small bumper/spoiler to buy, or a way to cut or trim some of the bottom of it so it doesn't bottom out and rip the bottom of the spoiler/bumper up???