Its not that hard, I can help you once the time comes that you want to prepare to test your new board…
I would use a bit more of the range, personally…
Certainly, you can. The three pin configuration permits some extra options like external filters and feedback. But you can also rely on the internal circuitry.
It will be easy to comment on all this once you have a schematic for your board - then it will be possible to understand the analog part of the circuit in its entirety and give meaningful feedback. Before that everything is very hypothetical. So yes, hypothetically 2 pins will work 
From the point of view of SimpleFOC it isn’t needed and currently isn’t used. But it’s on the roadmap for the future. Again, same thing goes as for the current sensing - we’d have to see a more complete circuit for what you intend to do. It might also be a strategy to design it and layout it but not include it in the v1 of the board? I think you’ll find that for 50V-80V it will be quite complex, involving either isolation or buffers, and therefore also costly for something that isn’t even supported yet.