Excellent chapter, but Hermione and Luna better have a little talk with Harry about force choking...... he might not become a Sith, but evil can snag anyone if they aren't careful! On the other hand, he hasn't force choked anyone who doesn't deserve it! I'm looking forward to seeing Harry teach Luna and Hermione how to use the force and lightsabers! Maybe Dobby could learn too! He's about the same size as Yoda! :)
I think this is the last time he uses that particular trick. I look at it like a police officer using a tazer instead of a gun. As you said, he only used it on those who deserved it. In each of those cases, Harry could have stopped his 'victims' hearts without being caught.
Moreover, this version is not 'dark' per se, but he has been shocked in to awareness by Dumbledore's allowing Vernon to beat him to death, and is not unwilling to use some darker methods in order to force through the changes he promised in chapter two.
As you've seen, Luna will get to play the part of Jiminy Cricket.
Dumbledore will most likely decry Harry as an up-and-coming dark lord simply because Harry isn't obeying his every whim.
You are quite correct. Hermione, Luna and Dobby will all be playing. Unlike most house elves, Dobby has an independent spirit, and a fierce loyalty to Harry. And yes, due to his size, his lightsaber will be very much like Yoda's.