Why should it matter whether or not "qualitative experience is fundamentally no different to the state of a Turing machine"? I don't see a claim anywhere that a Turing machine can't be conscious.

"but it must exist because my subjective perception tells me it does." seems like a rhetorical trick, consciousness is the underlying mechanism of perception, so it's not my perception of it that tells me it exists, it's the fact that I have perception at all.

As for a null hypothesis, how about this: "If my qualitative experience is no different to the state of a Turing machine, it should be possible to temporarily modify my mental state to remove all qualia -- so that I perceive nothing, but am still able to process everything" (In short, if I'm running code like sensoryData.processWithFeedbackTo(consciousness.Perception), it should be possible to do sensoryData.processWithFeedbackTo(null) temporarily)