Fisrt let me just say that this is a very good story, definitely original.
I have had a suspicion that Holly was Harry every since she got the journal, for various reasons mainly that Harry couldn't write back.
As for some questions for McG:
Why and how was I changed?
Who was in on the scheme and who knows about it?
Why give me the journal and who knows what I have written in it?
Just to be certain, my parents are James and Lily Potter right?
Whatever answer she/he gets to that question should be followed up with a demand that she gets every left to her/him NOW.
What happens now?
Are we going to tell everyone?
Those are just a few things that I would like answered and I suspect Holly/Harry would as well.