1) Making public information about how he created his cold wallet, or how it is stored, or where it is stored reduces his security.
Security through obscurity is not security.
3) Making them public reduces the effort of a compromise from "breaking into his server, obtaining root access to change permissions on backups, copying backups, finding the password" to "finding the password". Regardless, no amount of crypto "magic" will allow parts of the encrypted data to be read or even verified, so it would be pointless anyway. Hashing and encryption are two very different beasts.
Why not ? Say you hash the account identifiers (maybe with a per-account secret), pair them with their balance, sum the balances in a nice report.
Anyone can verify they are in the balance list, no one can look my balance up, I can check that the sum is consistent with the amount in cold storage.
That can also be seen as some sort of backup if properly signed, I'm sure the Bitcoinica folks would have loved to have something like that lying around.
