Hello there! I'm sorry about the wait, it's been a busy week revising for exams :/
Anyway, here goes!
I like your summary - it's very intriguing, slightly mind boggling and very magnetic in that it draws attention.
So you wanted to know about the style, characterisation and first person POV, and I think you've done brilliant with all three.
Characterisation: I really get to feel how empty and lost George feels without Fred, his emotions are perfect and almost exactly how I would imagine mine might be if I lost a sibling, but George's are possibly even worse, because he not only lost a sibling, he lost his twin. I think it's difficult to compare this George to canon-George, because we only really see George when he's joking around, and obviously he no longer has anyone to joke around with. But I think you've done a brilliant job, and he's pretty much how I would expect him after being through such an ordeal. Ginny was also very much in character as she helped hold Fred.
Style/POV: It has a really angsty feel to it, and I am of the opinion that angst is best written in first person, especially with this amount of emotion. It would be extremely difficult to completely immerse the reader in the characters feelings if you were using third person POV, so I think you were spot on there.
I think you've done a fabulous job with this chapter, I know it's given me a clear and realistic idea of George's feelings, thoughts and emotions about the battle and Fred's death, which we are never told about in the books, and which haven't been written about in huge detail - possibly because it's an awful moment, and I know I couldn't bear to write such powerful emotion, just reading this brought me close to tears quite a few times - but you've managed it fantastically, and I think it's a great start to an interesting story.
One thing I began to wonder about as I was writing this review, was Angelina. I know she may not feature in your story, as it is based mostly on Fred and George, but since she was Fred's (ex?)girlfriend and then married George, the events in this chapter are ones which could almost explain how they ended up married. Obviously they are similar - they're identical - but the whole being Fred, when he's actually George thing, I think that there's something there about his grief that Angelina could have helped with or fixed(I really can't find the correct words,) it's a bit difficult to explain, but basically what I'm trying to say is that this chapter could very easily fit in with what possibly could have happened in canon. :D
Altogether, I thought it was amazing and fabulously written(I salute you for that) and I am really intrigued and interested to see where you take it :D