A wonderful chapter. Harry's meditative explorations into the magic surrounding him, bring forth a dedication nnot seenn in cannon.
Blood sacrifice wards created by both Lily and James, is not new, but here you have also brought out my own arguments with canon. Dumbledore emotes on about Lily's sacrifice, yet says exactly nothing about James'. He placed himself in Voldemort's path to Protect those he loved. He died for Harry every bit as much as Lily did.
The energy trap represented by the wards around Privet drive gains it's power from Harry's magic? There is a very new twist.
Your explanation of the feedback creating a stronger protection makes perfect sense, energywise, to me...as does your reasoning on why it failed. Petunia&Co. have no love at all. Not for themselves and certainly none for Harry. In electronics terms, this is called a 'short to ground'. The energy ends up wasted. Too bad. If the Dursley's had taken better care of Harry than they did, they would have been protected from a friggin' atom bomb.
Since I despise Dumbledore's character anyway, I'd strongly suspect he knew ahead of time, both of the antipathy between Petunia and Lily, and the most likely way she'd treat Harry. My assertion has always been that he placed Harry there in order to train him to be a mindless and mallable sacrifice for Dumbledore's 'greater good'.
Knowing of the power drain, Harry has removed the link from his magic to the wards around #4. While his decision may be, in part, emotionally motivated, I don't see it as particularly ruthless...simply efficient. Instead, it's a matter of cost -v- benefit.
Harry is carefully following the scientific method: Carefully removing one aspect from the experiment and observing the result.
Alorkin
Author's response
The way that I see it, the wards around the Dursley's don't directly gain power from Harry. They gain power from the protection that Lily and James set up around harry. Those wards were suppose to be self sustaining but they took a beating when they were hit by the AK, then were further strained by Dumbledore attaching them to the Dursley property. The wards are being drained dry so they link to the closest source of energy. Also, that is the only place where it was just ripped away as opposed to collapsing from lack of energy. The other areas with empty space will have the 'ghost echo' of the lattice that can be filled in, this area is going to be wide open. That will pose a problem when Voldemort shows up. There isn't an actual connection between the two right now, but this area will already have an imprint of Voldemort's magic making it predisposed to creating a connection between the two at his resurrection.