Artificially sustained nuclear fission was, in 1923, not-well-understood and thought impossible; radioactive decay had been observed but the idea of chain reaction had not yet been conceived (it would take another 10 years). Natural nuclear fusion we currently know to be possible in the sun, but we don't yet know how to sustain it artificially today. Digestion was not-well-understood in 1823; although they knew that it was somehow similar in end result to combustion, which could be imitated artificially, they did not know how to replicate digestion on the chemical level. Now we do.

Consciousness is irrelevant, as it's clearly not necessary for AGI nor even human intelligence; otherwise you wouldn't say "it's not even possible to determine with any scientific certainty that another human being is conscious."

On what grounds do you believe that there are capabilities of the brain that cannot be replicated by a computer? When I look at the 1.5 kgs of matter in a typical human brain, I don't see anything that jumps out and says "my operation is not computable!"

At least with fusion, the high temperatures and pressures are a clear barrier. Our brains don't need to be held at 3.8 trillion psi and 15 million Kelvin in order to enjoy poetry.

I can certainly argue on the other points as well (breaking free / deciding threat / acquiring means) but you need to pick your goalposts one at a time. I think the first step would be asking yourself: if you were a super-genius but being held by guards in solitary confinement on a remote island with only a supercomputer connected to the internet, how would you earn money?