Scott, RVD questions:

How over was RVD during the Invasion? If WWE pulled the trigger on a title run in the three way with Austin and Angle rather than in 2006, what was his ceiling? How “high” could he have gone and what would his career had looked like in WWE if the run had happened at his peak in popularity?

He could have gone, like, really high, man.  You know?  Like instead of Austin 3:16 shirts he'd have RVD 4:20, man.  Far out.  
Anyway, yeah, they fucked up by not pulling the trigger on him sooner.  Or, if we want to avoid the whole discussion of whether he should have gone over at No Mercy in the three-way, he should have at least not been put in that match.  However, he 100% could have beaten HHH for the Fake World title in 2002 and carried the belt on the RAW side.