Hey Alpheratz,
I exchanged few messages wit YellowSubmarine and he gave me few advises how to solve CTD issues.
Please try this updated version of New sextant mod and tell me are those CTDs on gamesave/mission loading eliminated. I added your Polaris and stars tweaks to the mod as well... It seems that it works for me...
https://www.mediafire.com/file/akhub..._v0.1.rar/file