No worries - what you’re wanting to do sounds very useful - I notice things like that too and it can be distracting.
Yes I found navigating around a scaled solar system took a long time - in the end I had 2 distances in each “body”, one close to the sun for quick nav and the properly scaled one and changed the blueprint to whichever I was working on. You can also double-click the planet/moon in the World Outliner and it will take you there - but adding lots of cameras positioned exactly where you want them works better and you easily select them from the viewport menu.
Calculating the positions on a date/time shouldn’t be that hard either - you could just find the exact rotation at a certain point of time in the past and use that as a reference, same with the moons - just a lot of data for all moons on all planets…
There’s this asset on the marketplace that has all the brightest stars and constellations all calculated in realtime from stellar maps - referenced from on earth:
I get the feeling your going to have a lot of fun working on this!