Is there a way to add the warranty back on your device so I can fix my cracked ipod touch?

You can ot "add a warranty back" and it wouldn't help anyway because accidental damage is not covered. Apple doesn't repair it. If there is no sign of abuse, they replace it with a refurbished unit. The fixed-price for non-warranty replacements can be found here.

No. You can add warranty to a device. Besides that the warranty does not cover cracked screens that is considered damage