I am having the same problem with my space opera. I have a pov from a member of an alien race and then had a problem with how to describe distances smaller than light years. In the end i stuck with familiar terms like kilometres and flagged it as something to be changed in the revision stage after a little more world building. Unless you already have a finished draft, I would suggest you stick with your original terms - after all maybe some of that was what inspired you - and just get that story done. Story trumps everything.

Personally, I am not so keen on antiquated words for common everyday objects, as it brings me to a grinding halt in the narrative, while I wonder how that word should be pronounced. If you do retain them, then I think you should have a good reason for doing so reflected in the narrative and maybe those terms kept for something less everyday.