Sorry, what you did not consider is the 2+ million violent crimes that did not take place because the bad gun was stopped when they became aware someone there would shoot back.  Also, the number of people killed when there is a "good guy" at the scene is about 2.x  where when you wait for police to arrive it is more like 11.x.  
There are 11 million known/licensed concealed carriers today and crime (including gun crime) is a a 51 year low.  So, I suggest that your "study" has more than just casual flaws.