An excellent post. You pulled together a lot of evidence that supports what I've been saying for years about bloodbending and contextualized it with deeper lore concerning chi and the manipulation of it. Bloodbending really is the highest level of skill among waterbenders. It both demonstrates the highest level of skill at controlling the opponent's movements and the greatest degree of knowledge of how to manipulate another person's chi at the same time.And Amon took it to a whole new level when he showed he could shut off peoples' access to their own chi. Terrifying.As far as Aang not breaking out of Hama's grip I imagine the fact Aang had no idea what was going on at the time played into it too. He was confused, terrified, and had Sokka's sword pointed at him for most of that fight.As with all things in the series I'd surmise that a bender, no matter how great their chi is, most likely needs to know what is effecting them and how to potentially counter that before they can. Katara could do it because she'd been learning from Hama and was aware of what Hama was doing to her where as Aang was entirely ignorant to what Hama was doing.