Is it raised or concave? Tough to tell with the pics. If its an impression i would say bag/contact marks from the reeds of another.
It looks like the clashing of the Eagle's wing on the reverse die onto the obverse die. Pretty cool how it goes around the mint mark.
It's not the wing, but now that I look at the pictures it looks like the moon just East of the mint mark in pictures 1 & 2. I'll have to look closer when I get home tonight. Could just be a stain.
Depends on the die alignment. 180 degrees is the goal - sometimes they're off 10+ degrees. Could be die filing that wasn't removed by proper polishing.
Those are the result of a rotary die polishing head skipping over the die due to sloppy and quick polishing work. Just die polishing marks. Similar to the "Tiger Claw" http://www.ikegroup.info/?page_id=53