I believe in Hypotheses 2-4. I'm not saying I have understood all details either but here is why I think what I think:
contra 1) and pro 2) for the same reasons:
The dollar might have retained its purchasing power the day after gold pegging was abolished. Now, 40 years down the track, I wouldn't claim that anymore. Once an asymmetry between long and short holdings is introduced, I would think the price will lean that way too (slowly).
3) and 4) both are true.
The weaker one will be cancelled out. Risk will be considered less and less after time, I assume, so 3) wins.
Convenience (divisible, private, instant transfer) will have a minor effect, above market interest rates will pop the ceiling out. If short sellers have to pay high interest they won't short, not even high above parity.
… looking forward to the big experiment.