Another thing to consider is the heigth at which you have your guitar strapped on at....this could be why you lose control when you get to the lower strings, becuase your arm is in a akward position. A good rule of thumb is to adjust your strap so that the guitar is in the same position as if you where sitting. I know it looks cool to have your guitar slung low, but it is not always practical.

1 more thing..the thickness of your picks. If your trying to play long fast runs your pick may be too flimsy to respond in the way you want it too...try messing with heavier pick gauges.