These are un-cropped frames from my sigma 8-16mm f/4.5-5.6 at the 8mm setting on a Pentax K5IIs with HSM in use. There is clearly something wrong with your lens, the lens hood shouldn't be visible at all in the image. I think there is a distinct possibility that the optics are de-centered* and the lens information contacts could be also misaligned - this would explain the intermittent AF and lens/body communication issues.
Also it is perfectly normal for Pentax DSLRs to not have the 8mm setting recorded in the EXIF....annoying, but normal for this lens.
*I went through several different copies of the Sigma 8-16mm to find the one I currently work with, Sigma actually sent me a letter with the final lens they sent to me stating that it was certified by their technicians to be free of defects.