formatting one of my main harddrives with the command "dd if=/dev/zero of=/dev/sdb"
I see you like being thorough 
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But instead I will just tell you that the backup I had of one of my bitcoincore: "wallet.dat" files (yes it's the one from above...) is corrupted and now I ask for help.
Let's start from here: how did your backup get corrupted? I often read this, but in general digital files don't just get corrupted out of the blue. Something must have happened to it. "Corrupted" can be a lot of things.What version of Bitcoin Core were you using when you last used the wallet.dat before you made the backup?
Are you sure you didn't make another copy you've forgotten again? It's a long shot, but you wouldn't be the first!
As far as I know, https://walletrecoveryservices.com/ can be trusted. He's specialized in password recovery, but he might have some tricks for corrupted wallets too. I suggest you send him a message.
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I have absolutely no Idea if this wallet is recoverable at all, or if it is even worth the try.
It's always worth trying, you have nothing to lose, and at least an experience to gain.Quote
Or just extract the private key in a read-/spendable form.
One way or another, this requires your password. Be very careful to whom you send both wallet and password.Quote
As this is about a great sum of money I would need someone to Escrow this, as I am not up2date regarding this, I am open for suggestions on the "who and how", about the Escrow part.
I'm a bit surprised with the number of people offering rewards to rescue their coins lately. In general, people are willing to help without rewards, but you are of course free to offer rewards.I'd say OgNasty is trusted. It'll cost you 1% of the escrowed amount as a fee. I just don't think a $12000 reward will get you any better answers than a $1000 reward.