I don't know. I think that before Dean was sixteen, most of his identity and time was occupied with parenting Sam. Sixteen is right about the time when Sam would have been more self-sufficient and Dean would have been craving more freedom. As Sam needed Dean less and less, Dean shifted his identity from being like his mother to being like his father. I think part of what makes Dean so interesting to me is the way he integrated both parents into his identity. He actively and at least partly consciously took on both roles and aspects of both personalities.

I think when he was looking into the fire after that hunt, Dean was thinking about the kind of future that was possible for a guy like him, and who he could be once Sam didn't need him all the time anymore. If he couldn't be Mary anymore, all that was left for him was being John.

If Dean ever did yell at John, I'll bet it was about Sam. And while I'm intrigued by the idea of Sam as the good kid and Dean as the rebel (you're right, there should be fic!), I have a really hard time seeing Sam as anything but a snotty kid. But maybe my mind has just been poisoned by the fandom. Sam is ALWAYS portrayed as kind of a snot. :/