I had believed Halbrand was Sauron until about the third episode.

After episode six, I'm back to thinking he's Sauron and not one of the nine.

They want you so badly to think he is an Aragorn character. It will make the betrayal that much harder on Galadriel. Especially because they hinted at some "romantic chemistry" in episode 6 (eyeroll).

In the first episode, Gil-Galad and Elrond said if she didn't leave for Valinor, she would unwittingly bring back Sauron.

She set up Halbrand to be the King of the South. She helped him defeat Adar so he not only got some revenge on him for whatever Adar did, and he also can take over as the leader of the Orcs.

He asked Adar if he recognized him. So it's clear he is in disguise or different than he was before.

Finally, he helped Galadriel capture Adar, and it would have been possible for him to switch the key with a hatchet.

I don't think meteor man is Gandalf. I think he's one of the Blue Wizards.