You have a wonderful storytelling voice. Tolkien had the same, which was why he could write such epic distant omniscient, but because you are concentrating primarily on two characters, this comes across as more personal.

I was just thinking the other day that I had read no story that dealt with Erestor's history - not that they are not out there, but that I have never read them.
I also love stories that are deeply grounded, beginning at the beginning, and setting a strong foundation for the character, especially when very little is known about them. I can rarely become interested in a character whom is barely written of in canon plays a major role - emerges onto the stage as it were - as I have no history for him (or her) There are some canon characters where this works since we know where to place them (Glorfindel in LOTR being one example, if we believe he is Glorfindel of Gondolin) but Erestor is not one. He needs some created history.
Backgrounds are important to me and I find this one unique and engrossing.