Good call with the ProRes 422 HQ. I've only started working with Final Cut this year in my experimental editing class, but for shits and giggles I ran a comparison test between ProRes 422 and ProRes 422 HQ, and I can tell you that the HQ looks quite a bit better.
Other than that, everything else is a bit over my head! Though I did download your sample, and while you're right that there isn't that much noise, there is a difference between the 5-capture average and the single capture, subtle though it may be.