What matters is the "socially-necessary" labor

Yes, that's still classical Marxism, isn't it?

But the question is, what does using this framework give you? Which falsifiable predictions flow out of it, predictions which are contested by mainstream economics? As you recall, Marx predicted how history will develop and he turned out to be wrong.

Your answers tend to follow the first iron law of the social sciences: "Sometimes it's this way, and sometimes it's that way." and sure, the future is uncertain, but then why is the Marxist theory of value better than any other one?

I appreciate you giving a specific scenario for the world economy, but it looks entirely mainstream to me. I doubt you will have trouble finding conventional economists who will look at it and nod, saying "Yep, that's very likely". Though you might keep in mind that post-2008 the central banks around the world have dumped huge amounts of money into their economies, amounts that many if not most economists thought would trigger significant inflation. And... it didn't happen. At all. So that "fear of depreciating paper currencies with respect to commodity-money" could be baseless. Or maybe not X-D -- macroeconomics is really in disarray these days.