The DNC does appear to have been for Clinton but I think this is played up a bit much. She still did win most of the primaries. One can make a case for the issue with super delegates but that is not something that can be manipulated easily. Clinton would have always had an intrinsic advantage with that one.
I liked Sanders more than either of the others. I am not sure he would have won either though. It is hard to say exactly how things would have gone but I doubt too many American's want to vote for somebody who states they are a socialist.
He definitely seems like a kinder and more grounded guy than Trump. He had his own issues though.
The Wikileaks Emails pretty much confirmed it. News outlets were reporting it after the election.