I don't think it's a vg10 thing, more a shun thing. I used to have a shun and a few work colleagues have them, keeping it at 16 seems the best bet, with good thinning behind the edge. Although also had em at 10 degrees and it held a lot longer than you described... On poly boards. Maybe focus your efforts on the final stages on sharpening.
I agree with everyone that said maths to determine angles is pretty unnecessary although I can see how it would appeal to some. A rough estimate with some paper plane folding skills will do the trick :) many other things are more important than calculating angles to perfection ... Just my 2 cents
Here's a photo, the shun on the right is one year old, quite a few scratches from diamond steel abuse
Shun on the left is 7 years old , sanded with wet and dry 400, 800, 1200 then metal polish .
AS mentioned auto wet dry paper.Start with finer grit see if it takes out the scratch,if not go to a lower until find grit that removes them,inspect the blade make sure they are all gone.Then go to finer grits to finish.It's not that much work as long as the scratches are lite surface ones.Be aware that you are working with a sharp edge edge,I like to wear leather gloves while doing this kind of work.