So if I understand you correctly, you need to push the saddle back another half inch - why not just loosen the bolt, nudge it back and then tighten it back up again? The bolt is pushing against the leather underside so it shouldn't affect comfort too much. At the very least then you will know if moving it back is indeed the right position for you.
By the way, well done on the photos! They clearly illustrate the problem you are having.