You hit on some real issues that I think derive from "it's software" and "it depends on people's right thinking and acting in order to work." Both I guess derive from "the social." Gold still needs some other person to accept it as payment, but that's about it. Neither party even needs to know why it works or how it works or to depend on other people's actions. I think of myself as pro-bitcoin but gold is still better in the long run. Of course, the dollar is garbage compared to either.
Discussion
Gold needs much more than some other person to accept it. At what exchange rate? What is the total supply? Who verifies that in a trustworthy way? How does supply adapt to demand? Are there large deposits we haven’t discovered? How do you guard it, transport it (internationally)? Where can you safely exchange it in times of government oppression or depression? How do you verify its authenticity and at what cost?
With two parties, whatever exchange rate they prefer. They don't need to worry about the total supply but if they're curious, sure. Supply and demand work as usual: subjective value on the margins. If there are large deposits somewhere, they pale in comparison to total mined supply. Yes, you do need to guard it, kind of like your keys. The safely exchange question applies to any honest money, but if you already know a that second party who will exchange, you're OK. Authenticity is a legitimate concern.