Have you considered that perhaps there is something wrong with either your camera or lens? Maybe worth getting Pentax to check out.
My K-5 requires minimal or 0 AF fine adjustment for most of my lenses.
And for reference, a friend of mine (non photographer) took this picture - he wanted to try out my camera, and effectively just pressed the shutter button in Green mode.
FA43Ltd: shooting conditions are f1.9 t=1/80 ISO=800 (so EV is approximately 5) in a restaurant with halogen lighting (JPG, no additional processing):
As you can see, her fingers and chin are out of focus, as well as her hair and jacket, but her eyes are focused, so I would say the AF is pretty spot on in that photo.