Hey, the plot is really intriguing. And I really liked Dumbledore's history in the 6th chapter. I mean no offence but the story could do with a bit of polishing. The writing could be a bit more encapturing.(I don't know how good is mine, but my beta really helped).
I suggest you ask someone to beta the story. They will provide valuable advice. English is not my native language or else I would have tried to help a bit more. And post it on ffn and siye, where many people will be happy to give advises.
I hope I didn't discourage you. The plot is really good.
All the besy