Good description of Snoke as the only adult in the room. You're right that Hux and Ren are dangerous, but because both are very not ready for prime time their reign of terror won't last long. Palpatine, Tarkin, the old Imperials, were far more methodical and felt really dangerous (granted I'm still looking at it from a nostalgia angle, but I still think they hold up as legit villains). I think Johnson had to pretty much wipe out the Resistance, reduce their numbers so much to make the First Order credible villains. And even in TLJ they snatched defeat from the jaws of victory. I can see Hux plotting against Ren under the table but not openly challenging him, so I'm skeptical that Hux would form a competing faction. Ren put a stop to that when he force choked the crap out of Hux in TLJ.
I hope they use the opportunity to feature the Knights of Ren, perhaps as Kylo Ren's enforcers, and also an administrator, like a Moff, to give a hint of how the First Order is run.
I would like this other apprentice to show up and be more of a legit threat. Perhaps even a Sith Lord. Make the character a female Sith, which would be a first in live action, and in keeping with the female-centric nature of the sequels. As it stands, I don't see how or why Ren would return to the dark side (and I can't see Disney not building on his relationship with Rey, since it's Abrams coming back and he's not the arsonist that Johnson turned out to be).
Like you I think there will be a time jump, though I'm thinking more like two-three years.
