<<Yes ,if any of that were true , and I am not sure any of it is , McCain would still be left with the burden of proveing that there was malicious intent .>>
The beauty of suing, if McCain really didn't say it, would be that he doesn't have to prove malicious intent because he doesn't have to win the case. He's not in it for the money, he'd be in it for vindication.
Schecter would LOSE the case if he didn't name the sources because, according to BT, he's a political operative rather than a journalist, and they'd have to testify even if they're journalists because McCain didn't communicate anything to them in confidence.
So for an innocent guy, McCain can't lose this one. If he really isn't as innocent as you claim him to be, he has a lot to fear from a lawsuit.