I can try answering some of these (even then, I'm doing it in basic ways) in order to not be confusing to other people later on.
As of the time of this message...
2. The TerrainFormula settings take care of that part.
3. Usually that's made using gradients, textures, and stuff in a 1 by x grid (x must be less than or equal to 16536 pixels tall). The idea is simple but the execution is rather... Dragging, for a lack of a better word.
5. I believe that's due to a limitation in SFS's orbit line rendering, which happens at around 1 ly in the scale of SFS 1.4. But the objects are still reachable.
6. For this specific parameter, its more for the eventual case when the orbits get soo eccentric that the orbit quality ends up dying. Say, Hale-Bopp. So you can end up increasing the resolution until the quality of the periapsis actually looks like an orbit.
7. I'd either look at the Kopernicus wiki, a Google search for each of the objects, and/or reproject each of the textures in the OPM mod into a sphere for spherical objects. (GIMP <3)
8. Start from searching on the internet, then eventually learn how to make then yourself using tools like PDN, GIMP, or your 3D rendering tools. This is more of a question that changes over time as you learn more.
9. The object count where this point hits depends on the device, but its inevitable, unfortunately.
1, 4, and 10 are currently a bit beyond my knowledge at the moment.