I don't shoot well enough and my release isn't crisp enough to paper tune my recurves and longbows. Any arrow should make a bullet hole at 15 to 20 yards no matter how terrible the bow/arrow is tuned. I have to bare shaft tune my bows.
Nothing wrong with the distance. Your gap would be less at 10 than 20. The right/left issue could be many things; arrow not directly under your eye; arrow too stiff, and other things as well.
If you find your point-on distance, you can easily plot your gap from zero to that point-on distance. At 1/2 of your point-on distance you can measure your widest gap and plot it from there.
Jim