I have no idea why you consider "Elricest" to be a pairing that needs more exploration. It doesn't and if I never saw another Elricest fic in my life, it would be too soon.
Taking straight characters and making them homosexual would have gotten you a big "OOC" rating alone; the fact that the two are brothers was the final nail in the coffin. I could -never- imagine Ed or Al behaving the way they do in this fic.
The only redeeming factor in this story was the fact that your grammar was perfect, as far as I could see. You don't seem to need help with the technical aspects of writing, however, I suggest that you really think about the characters you're writing about next time. Just as a starting point:
Would two brothers really be "in love" with each other? Where do you find any evidence in canon for this?
Would Noah's behavior toward Ed in the movie give any credence to her attitude here?
When has Ed ever been "normal?"
If you feel the need to write about two brothers who are in love with each other, why don't you try writing your own, original fiction that deals with the subject? Then you have the creative license to do whatever you want! Fanfiction, however, has certain rules and one of them is: The characters you are writing about should behave in the way the original author created them. If they don't, they are out of character and it doesn't matter how letter perfect your grammar is.
And regarding your author's note at the end of the fic, there are some things that A/U doesn't excuse. Incest is one of them. And if you're going to change a character in an A/U, you need to back it up so the reader can see where you're coming from and how X character might have reacted in Y set of circumstances.