You're right on all counts!

Part of the challenge is creating something manageable...

1000x1000x1000, even, is 1,000,000,000 sectors....which brings my computer to a crawl just trying to manage the "sector" coordinates list...

My thoughts tend to be on the lines of a 100x100x100 blocks, that then fit into a larger coordinate system, as necessary.

p.s., for those interested, apparently the current thinking is that the universe is actually expanding at an accelerating rate - not slowing down and ready to collapse again, as I was taught many many years ago. Apparently cosmology has, well, changed and learned a lot in only the last 15 years....