[Christ]

Will,

If the new rings create a total seal with no obvious gap, then they're fine to use. With a single compression ring, the fear is that there will be obvious blowby from combustion, putting mixing combustion gasses and oil.

As far as that area in the cylinder, if the piston rings don't touch that spot at full travel, probably not really a big deal (unless you're anal about cleanliness).

Technically, the skirt will rub against it, but as long as you oil the piston skirt before you put it in there, it should be OK and will polish that spot.

Your cross hatch looks pretty good for apparently never having done it before.