Re: part 2 D. and M.'s actions are a different matter. Looked at it this way, none of the books makes any sense, since they should never have encouraged Harry in his endeavours. But then, it was all training for the sacrifical lamb, with collateral damage accepted, wasn't it?
No, I don't think their favoratism was all because Harry was to be a sacrificial lamb. A lot of his treatment appeared to be favoratism to Gryffindors. There is no evidence that McGonagall knew about Dumbles' plans, but she still had no trouble breaking all the rules to help out Harry every chance she got, including putting him on the Quidditch team in violation of school policy and rewarding him for rule-breaking.
About the first potions class...I look at it a little differently. Harry compares Severus unfavorably to Flitwick because Flitwick made a fuss when he got to Harry's name on the roll, while Severus referred to Harry as their new celebrity at that point. Severus then finished the roll and gave his opening remarks (similar to McGonagall's remarks) before asking anyone any questions. And Severus' criticism of harry to start with is just to comment that Harry apparently didn't think he needed to do the reading before class.
While you say Harry didn't provoke Severus, keep in mind that Severus initially did not take any points from Harry. And when he did, it was because Harry instructed him to ask his questions of Hermione rather than Harry, and then limited it to one point.
Mind, I'm not saying that Severus is a wonderful example of a teacher. But it's also not fair to say that Harry never provoked him. Showing up unprepared and then mouthing off is not exactly unprovoking.