If it were me, I'd not kill myself trying to do this perfectly. Getting the atomic transaction right, along with the cascading deletes, etc. seems to not be worth it.

Have you considered relaxing your requirements a bit so that the delete will work correctly in all but the most extreme circumstances, and then just running a periodic maintenance job to make sure you're clean on files-to-pointers and pointers-to-files?

Perfection is cool, but can be dear to implement.