Pixel scale in PI is not the pixel size of the camera. You can find out the pixel scale by uploading your FITS file at http://nova.astrometry.net/upload
On the results page, you will find the right number. Just wait until processing is finished. This might take a while.
And btw: it is astronomy.tools, not startools.com and this will tell you if your camera/scope combination produces correctly/over-/under- sampled images.