A few minutes after I stepped away from the keyboard, I had a revelation about your story - something that was probably obvious to you, but which just seemed like an odd non sequitur to me until now. My alter ego in your story doesn't just think that he sees a black disk, he thinks there's a black disk literally floating in front of him all his life, which is why he goes on about momentum, yes? I had thought momentum was just thrown in there as a random physics buzzword. And so your alter ego is doing nothing but explaining that hallucinations are possible, I think.

This is coming at the problem from the wrong level. The experience of blueness is a problem for physics whether it's veridical blueness or hallucinated blueness. Either way it's there at the level of experience, and either way it's not there at the level of neural physics. I will answer your four questions tomorrow, if you still want me to, but I think you're not engaging with the challenge here. Unless you intend to maintain that the whole of humanity's experience of color is unreal.