I may to have to jiggle the date, as so many of the words we use come from C14th
I wouldn't worry about being too strict - just avoid anything too jarring.
But as to this piece - I do really like the voice. Only a couple of places where I might have personally snipped, and I would like a little more pace - but you'd likely address that after a finished draft.
Personally speaking, I think you're onto something.