Now, I am going to be a bit coy and just try to answer your direct questions.
The original cast is largely back, with few exceptions. Reunions are bittersweet when they occur, although some of the characters are spread out from one another.
Luke has a baker’s dozen students, we find out.
The main bad guys are sort of an Imperial remnant that gets radicalized under the influence of a Palpatine(like) figure.