I'm having trouble telling whether or not I need a new type of reed. Right now I use a 2 1/2 Vandoren. However, I only like the new ones. After playing once or twice on them, they get an airy tone quality and outright stink. Is it possible I need to go up to a 3?

It sounds like you should try a harder reed. I know that you can buy vandoren reeds individually (as in: not a whole box) in Denmark, so maybe you should try to by 2-3 reeds from your local music store