I disagree about the Mr. McMahon character. The seeds of the Austin vs McMahon feud were actually being planted before the screwjob happened. Austin stunned McMahon on 9/22/1997. No one could tell me that they weren't already planning on this feud eventually happening.
Vince now claims, and has for years, that no one saw him as a heelish character until after the Screwjob but it was a bit more complicated than that. I think the Screwjob added towards the hatred of McMahon, but he was already getting heat and the Mr. McMahon character was already developing. If you go back and listen to the commentary he did between the time he was stunned and the screwjob, you can see they were leading toward this eventually. So I think Austin vs McMahon would have happened no matter what. But I do believe the screwjob excelerated it.
WWE would still have surpassed WCW. WCW began a steady downhill slide ever since Starrcade 97. It was in 1998 when they began putting on stupid, stupid shows and their demise was largely their own fault. But it may have taken a little bit longer for WWE to get their foothold back.