This is quite interesting but definitely AU. You give hints of a Dark Harry (with all your references to and posting on the Dark Harry site). But perhaps you don't realize that so far you've really managed to come up with a Dark Dumbledore and not a Dark Harry. Oh yes, Harry is using Unforgiveables. But I rather think that Wizrard Society (as you do in a bit different way) would develop something on the level of justifiable homicide. But then perhaps that is why the Wizards seem to have so much trouble with Dark Lords -- the Wizard "police" don't have an effective way to deal with them with their hands tied to using stunners.
Your depiction of Dumbledore has gone down hill from you attempt to present two justifiable positions. Dumbledore is now reduced to little better than a petulant old man who is upset that he isn't getting his way.
Well thank you for the comments. Sorry you don't think much of Dumbledore in this story. Hopefully, it will change later.~Jim