Sounds like you're having to keep with the civil war re-enactment requirements. As others have said, consistency in your stitches is the most important thing but the 'old' 9-10/inch is still pretty 'standard'. I'm not familiar with a quilting 'table' so not sure how that will work for you. If you have the option of sandwhiching everything first, I use big 'binder clips' available at office supply stores. I place the backing wrong side up, centered on my cutting table and then clip all that down once it's smoothed. Place batting - smoothing and clamping as I go. Then the top, again smoothing and clamping. Since you can't use pins due to authenticity I would thread-baste the sandwhich. Starting in the center of the quilt, use long lengths of thread and loooong basting stitches to hold it all together. When you get the center all done, shift the whole shebang, smooth and reclamp, continue thread basting. Shift it all till you get the whole thing basted.
As to sharpening your needle, again for authenticity if that's the issue, I would use any of the knife honing tools available there. I don't think sandpaper or emery cloth was an option then - not sure. If so, I'd use emery cloth as I don't think it would create burrs on your needle as I think sandpaper might. Otherwise, I just use another needle when the first one got dull. Personally I like Roxanne needles but they have realllly tiny eyes and you really need to use one of their threaders to get most hand quilting threads through them. Their threaders have a finer metal loop than most others. Although the size 10 Roxanne's eyes seem to be okay for not needing a threader at all.
Your quilting plan sounds perfect. Sounds like it's just the right compliment to your squares. Good luck and have fun.