it's a stoner thought that for all I know is totally true, but it's so impossible to either prove, model or test

That's basically true for every hypothesis about consciousness, though. That's why it's called a hard problem. Like yeah, we can map neuron activity and record what the subject says they were thinking about. But that doesn't tell us what consciousness itself is.

And those "stoner thoughts" are how we conceptually narrow down the possibilities via internal consistency, and maybe get to something we can test. Just because we haven't developed a test for a hypothesis doesn't mean it's impossible to do so. And even if a test is impossible, that doesn't mean the hypothesis isn't true. It just means we can know whether or not it's true.

We don't really have models to compare too. We have hypotheses, but how do you test them? Is consciousness an electromagnetic phenomenon? Is it purely mathematical? Can it exist in gravitational systems?

We know precious little about the universe. We have snippets of data about our immediate locale, and ever-changing theories about our not-so-immediate locale. We are specks on a rocky speck orbiting a fiery speck on the outer spiral arm of a bigger speck.

Maybe consciousness is a fundamental force. Maybe it is emergent and the universe thinks a billion times slower and bigger than we do. We just don't know, and we didn't really have any way to measure one way or the other. That's the tricky bit about subjective experience.

I don't think it's any more "desperate" than any other theory. The only default position is solipsism: mine is the only real consciousness, and all the rest of you could be inventions of my mind or clever automatons. Once you start generalizing more than that, any line is kinda arbitrary. You either wind up at the universe, or you have to come up with a good reason to stop; and I don't think we have the physics to confidently place that line.

I think the definition of consciousness meaning "internal state that observably correlates to external state" would clarify here. Gravel wouldn't be conscious, because it has no internal state that we can point to and say it correlates to external state. Galaxies/the universe doesn't either, as far as we can tell. Galaxies don't have internal state that represents e.g. other galaxies, other than including humans in that definition, but it would be more proper IMO to limit the definition the minimum amount of state possible. You don't count the galaxy as having internal state that represents external state, if you can limit that definition to one tiny, self-contained part of the galaxy, i.e. a human brain.