I think I share alot of your theories...and I wanted to add 2 things that I have read recently. Please forgive me if I am repeating something already said.
1 Kreacher was suppsed to be cut from OOTP the movie..but Rowling told the producers that they should really leave him in..because he would become imporatant later on....
2 Helena Bonham Carter said that she received a note from Rowling before she took the role of Bellatrix stating that even though the part was small in this movie it would be huge in number 7....
Part of me wants to believe that Dumbledore is alive if only because of the way his death is described..he was thrown over the tower...all previous A.K. deaths were sudden and quick..grrrrr
BRING ON JULY 21!!!!