Damn, this is some really good stuff! Poor Harry, already making a bad impression on Dresden, and he just arrived. And owing the Summer Court not one, but two favors... I suspect he's going to regret ever seeing the Summer Lady. Though, if he keeps the power he gained from the Summer Well, he just might be able to wrestle himself from the Summer Lady's control, even with those 'geas' in place. He did snap out of the Imperious at, what, fourteen?
About Harry's power-level... After fighting for so long, he's bound to pick up more than just one trick, and he IS prophesied to be Voldemorts equal, so it is not very surprising. And, in a time of war, normal morals and ethics tend to not apply, so Harry knowing heavy duty combat magic is not strange at all, in my opinion.
He does have plenty of power to throw around, just look at his anti-one-hundred-dementors Patronus!
And with the dazzling and scintillating display of powerful magic shown by Dumbledore and Voldemort in the latest movie, I don't doubt your descriptions of magic at all.
Just hope Harry's got a freaky Animagus form, like a dragon, a Nundu (giant cat with a breath containing all the diseases in the world and requires a hundred wizards to subdue) or a basilisk or something similar, just further set the belief that he's an Outer Lord of the Darkness or whatever the heck they think he is into the heads of the Dresdenverse characters.
Maybe he was changed by the travel and now really is more than just human...
Time will tell, I suppose.
Keep up the incredibly good work!!!