I don't think making added bonuses for being in your favored class is a good idea. You're making it so people will choose certain class-race combinations for the bonuses so they won't fall behind the other characters and this will also make the human more attractive because of its open favored class.

It's late and I'm not typing what I'm trying to say very well. I guess all I'm trying to say is: Why do we need favored classes in the first place? The race's stats already naturally gravitate them to certain classes, so don't worry about deciding which class is liked by the most dwarves.