Agree with your points on the primary two questions and the circular argument in the original article. However, re: " How is it that atoms/electrons/photons suddenly start experiencing pain? What is it, in terms of atoms/forces, that's experiencing the pain?" that's an interesting question but not necessarily fundamentally refuting of #1. If you start with #1 "Consciousness is an unknown physical something (force/particle/quantum whatever)" then it has 'perceivable' properties of it's own different from those of it's constituent atoms or electrons. A toy example is the 'wetness' of water. If you only look at atoms and molecules with no way to 'experience' water then it's hard to conceive how water can have properties (though in the case of water it is tractable)

Consciousness *may* be something similar. If it is (e.g. the purest form of energy) then it is not inconceivable that it has some properties that not not tractable if we only look at more granular manifestations of it.

Agreed! I'm skeptical of consciousness requiring some exotic new physics (a quantum phenomenon or a new form of energy or somesuch) but we can't prove that it doesn't.

Honestly, if someday a scientist proves that consciousness is a fundamental force like gravity, I would say, "yup, that makes sense!" even if I don't think it's likely.