I’m glad you decided to drop the prequels. Those movies can’t be fixed. At least not to what we wanted / expected them to be.
My 2 suggestions to ROTJ-R:
When Vader grabs the emperor, make some of the lighting coming from the emperor reaches Vader (if possible with some sparks from Vader’s device in his chest, to suggest it was broken by the lighting). This way it gets more clearer Vader’s sacrifice and why he died (saving Luke cost him his life support). The way it is now in the movie it seems like he “lost his will to live” 😉
I think Luke should have gone back to Yoda to finish his training after ESB:R. Between the ESB and ROTJ Luke finished his training. While that was happening, the empire chased the rebels and when ROTJ begins, they are in really bad position, with the empire close to a final victory. That will increase the drama in ROTJ. A new crawl can set this to the audience.
Vader lighting up internally like a Christmas tree, the scorched smoking armor, and the “iron lung” clearly sounding like it’s damaged doesn’t sell it enough for you?
I may be mistaken, but IIRC you can’t see any lighting reaching Vader coming from the emperor, so I must assume he were using cheap chinese eletronic that broke for no reason.