Whatever you could possibly know and value about reality can only exist independently of the physical universe.
That is not what I am saying. I mean that things that we think of as tautologies, or purely logical truths, which are true no matter what universe we are in, exist independently of the physical universe. Facts about the physical universe are not in this class. Indeed, the entanglement of our physical brains with these logical truths is an example of a fact about the physical universe that, of course, depends on the the universe.
If your uncertainty about math doesn't indicate uncertainty of the math, and it's an argument for math being otherworldly...
You have my argument backwards. I first make the point that facts about math are not facts about the physical universe to support that the uncertainty we have about math, which exists in our heads, in our physical universe, does not exist in math itself. The argument does not work the other way, there are plenty of instances of uncertainty in our minds that are not uncertainty in the things elsewhere in the physical universe that they are about.
My comment was an attempt to explain why we need observation to believe things that are objectively true regardless of the world we exists in. Basically, we need evidence that our brains, existing in the physical worlds, are suitable for representing the logical truths.
David Stove's "What Is Wrong With Our Thoughts" is a critique of philosophy that I can only call epic.
The astute reader will of course find themselves objecting to Stove's notion that we should be catologuing every possible way to do philosophy wrong. It's not like there's some originally pure mode of thought, being tainted by only a small library of poisons. It's just that there are exponentially more possible crazy thoughts than sane thoughts, c.f. entropy.
But Stove's list of 39 different classic crazinesses applied to the number three is absolute pure epic gold. (Scroll down about halfway through if you want to jump there directly.)
I especially like #8: "There is an integer between two and four, but it is not three, and its true name and nature are not to be revealed."