Palpatine had incredible foresight and power, but he needed an apprentice to carry on that way of life when he died. He knew Maul and Dooku were only temporary solutions. Vader was "the one".
He was well on his way to becoming twice as powerful as Palpatine, but the lava bath really changed things. If you like "Dark Lord", then Vader figures out he can still be just as strong, but in a different way. Unfortunately he is a walking lightning rod and serves under a guy super powerful with force lightning. Therefore, he cannot take the Emperor alone. Still, in the Emperor's eyes, Vader is competent, but damaged goods. He sees in Luke what he once saw in Anakin, so both Vader and Palpatine originally had dark intentions for Luke.
Short answer, Palps needed an apprentice.
since the Empire was kinda split between people who were loyal to the Emperor (Jerjerrod) and people who were more loyal to Vader (Piett).
Ehh? Really?
Pretty much. The early drafts of Jedi had the opening scene roles reversed, with Jerjerrod being the one dishing out shit to Vader, and the two were at odds with each other for the remainder of the script until Vader choked him to death after trying to stop him from seeing Luke (by order of the Emperor). Piett remained loyal and perhaps sympathetic to Vader. That script was more about Vader trying to save his son than the other way around.
Also in the early drafts of Jedi: weird shit. By that I mean the ghosts of Obi-Wan and Yoda playing a part in the duel with Vader, blocking lightning, and eventually coming back to life. That draft left whether or not Vader was redeemed up to the audience as well, since he just tackles the Emperor into lava and they both die. Some interesting things from that draft though was the inclusion of Coruscant (then called Had Abbadon), and Endor was the forest moon of that planet, meant to be a parallel I suppose. Also, there were two Death Stars. Contrary to some rumors, Lando survived the explosion in every known draft of the film.
Here's a dumb question, but what would the tactical advantage of blowing up Endor be? Moff Jerjerrod was informed of fighters entering the super structure before he gave the order to fire, so even if they did destroy it, moments later the fighters would still reach the core. And it wasn't like Yavin where the centralized rebel alliance would be wiped out completely if the planet was destroyed. On Endor there was a only a small strike team.
Perhaps he hoped to do it in time before the ships entered the superstructure, or that his pilots would finish them off. Mainly it would've been to kill Leia, Han, and Chewie to cement Luke's turn to the dark side.