I keep getting delivery status notification failure for contacts no longer in my address book, for e-mail links I'm not actually sending. Any way I can stop this?
Not really, no. You are the unfortunate victim of a spammer that's using your email address in the from and/or fail-to fields in the messages that they're sending. I believe it's a way to try to get around anti-spam measures that check to see if the sending address is valid.
I've been the victim of some of these myself, at various times over the years. They usually calm down after a little while (or the Gmail filters get smarter).