How he would have voted if the Congress had considered and adequately debated a Constitutional Declaration of War as Ron Paul proposed? If the Congress had performed its Constitutional duty?
You don't know that, and I don't know that. What we know is that Ron Paul did introduce an alternative to the "Resolution", and that was to Constitutionally Declare War. How any GOP Representative would have voted on a Constitutional Declaration of War is but a phantom of your imagination, because Congress elected not to follow the Constitution as Ron Paul advocated.
Declaration or no declaration, Ron Paul opposed going to war in Iraq and repeated anti-war talking points in 2002 when the resolution was being debated.
http://www.house.gov/paul/congrec/congrec2002/cr100802.htm
He also gave this speech just two weeks after 9/11 when he said why we should understand why our enemies hate us.
http://www.house.gov/paul/congrec/congrec2001/cr092501.htm