One thing I hate, a minor thing, is that that Luke and Vader never swap lightsabers during their duel in ROTJ.
This is something I would like to do in an eventual ROTJ edit!
And I agree with you about the dark side thing. I definitely think the out-of-universe names derive from it simply being the good side and bad side, but I like to interpret the in-universe naming of the “dark side” as referring to the mystery and unknown aspects of the Force that the Jedi deem too dangerous to tap into. It’s a deep, dark well of knowledge that could hide unimaginable secrets.
I think Palpatine hints at this by referring to the “great mystery”, and wanting to understand all its aspects, but I think it would’ve helped get that idea across even better if Palpatine had maybe used a clearer allegory.