Yes, the tools and jack behind the seats under a plastic cover was a series one only feature.
Series two and up had the "cup" behind the badges. They are functional though! There should be an outlet towards the front of the car. Kind of like a side scoop but on the inside of the car...
Yes, both 1970 and 1971 cars can be a series one. The 1971 series one is usually referred to as an early 1971. Series one cars were made up until 1/71. Your VIN is awfully low to be titled as a 1971, although it is possible, just not likely. From what I've seen, the switch from being titled as a 1970 vs 1971 happened roughly around the 10,000 mark, as far as VINs go.
No, series two cars did not have hatch vents, ever. That's another series one only feature. So, yes, you are correct.
Wasn't my comment about the 260Z, but you are also correct. 240Zs and 280Zs were HLS30s in the US. 260Zs were RLS30.
A series one 240Z emblem for the C pillar is held on by two studs, side by side, ~1.5" apart. Not the triangle shape the holes would make with a later badge.
This pic might give you an idea, although it's kinda hard to see. It's the best I've got on hand though.