I've been a bad reader for not commenting on the previous 18 chapters prior to this one but I have been so into the story that I just can't not click on "next" and jump into the next part of the tale.
I am impressed by your word craft and I have no issues at all with the Old English/Rohirric speech in the past few chapters. As far as your use of the fyrd goes, it works very well with the Beowulf era culture that Rohan is based on. And yes, it was made up of yeomen and farmers and most of their weapons consisted of bows, cudgels, staves, spears and the like.
You definitely have your own voice in the way you write, a somewhat more active voice than J.R.R.T., but still having much of the flavor of the canon texts. The difference works beautifully with this alternate universe you've created; a different, even darker voice for a darker story.
So far, my emotions as I have read have run the gamut from sadness, to outrage, to joy, to open mouthed horror, to appreciation and everything inbetween. Nothing has broken my susension of disbelief from the first words of the first chapter.
I'm going to go back to reading now...