There's a category error in your formula.
You have government debt minus national wealth.
As if the government was the same as the nation.
...in the real world we got the US --with maybe a fourth of the world's wealth-- at $79T assets minus $13T debt and that = $66T net worth....
...You have government debt minus national wealth...
Let's get together on what we we're talking about.
The article looks like it's working with private net worth so that means we go to the link and get $13T private liabilities total from table B.100 page 113 (p. 120 of the pdf). No gov't debt involved. If you think the writer meant gov't debt you can say why but that's still not the point. The writer made up a $1.3Q number out of thin air and somehow that's supposed to mean everyone should buy gold.
Bogus.