Hey, thanks for sharing the detailed feedback!
1) Sins 2 combines the nebulas and star background into a single skybox, so it's true, that it cannot be disabled in the same way.
Possible solution could be to use a minimod which would replace skyboxes without the nebulas.
Alternatively, you could go to extended settings via ctrl+shift+s. There you could search for "sky", and disable the rendering of skyboxes. This will turn of the nebulas, however this will not be same to Sins1, as there is no secondary layer of dark sky, but maybe you'd still prefer this solution
2) I am not sure about this issue. In my experience selecting planets is easy. Only possible interference is when ships are jumping, and you try to select planet with the selection box, but capture ships. Otherwise a simple click on the planet, or selection box work perfectly fine for me
3) Do you mean the outline, when zoomed out? So the icons of the ships? Or when zoomed in?
4) In my experience, the search function is quite helpful, but yes, it does require some game knowledge. Otherwise, for technologies you could take a crack at the game guides. Very soon there will be even a detailed Advent guide, which does include overview of their technologies (it's not available yet, but stay tuned) - https://wiki.sinsofasolarempire2.com/space/SSEFW/2061041703
5) This one is a bit tricky, as your ships may get minor damage all over the place, from some raiding forces, bypasses, etc. But I will share your feedback with the team.
6) Yes, the main source of exotics are the exotic refineries (unlocked in tier 3 of civilian tree). But there are other ways on how to get exotics. You can capture derelicts, survey planets, or ask allies for their exotics 
7) The Carrier cruiser is still there. It's unlocked in tier 2 of hostility tree, and can house up to 3 squadrons per ship. Note - you need to have a Greater Factory, to be able to construct them, because cruisers are built in the same factory, as capital ships.
Hope this helps!
