Oh and I forgot to add the important part:

I don't know if my results suck at $50 because I'm a bad player or because I've been unlucky, or because I played fewer tables and may have become impatient.

For smaller stakes games, 10PTBBs is crushing the game. When you get up to $200NL and higher, its going to be almost impossible to have a win rate that high, so anything around 8PTBBs is pretty damned good.

I have less than a handful of guys in my database higher than 8PTBBs over any significant number of hands.

According to my math, before your losing streak, you were at about +5.7PTBBS / 100 hands, so I would probably stay where your at for a while longer.