Regarding the identity of Snoke - I've figured it out.
So, Snoke was there at the end of the Empire, correct? He says (in the book) that he saw the final confrontation between The Emperor, Vader, and Skywalker, correct? And he looks badly burned and scarred. Therefore, he had to have been on the Second Death Star. That means he wasn't some outworld force wielder, such as the Nightsisters, or some clone like Joruus, but was there. It also then likely isn't some fallen Jedi, as the Emperor would have had none of that around him. So who was he?
I used to be the biggest Star Wars nerd that ever was. That was before the prequels, when the "cannon" of the Thrawn Trilogy, and the Jedi Academy books were so thoroughly crapped upon by George himself. It wasn't until a few years ago, when the Clone Wars brought me back in. Nevertheless, I knew a tonne about what was happening in the background back in the day. That's how come I recognized Snoke.
The emperor, on the Second Death Star, was consulting with a pair of diviners, or dark side fortune tellers. They appear briefly in the ROTJ, and it's actually not easy to find a picture like this online, but there they are. I'm guessing the guy on the right is Snoke.
Of course, my original thought is that he wasn't super large, either. That he was in actual fact really small. Like the Wizard of Oz. Or another character voiced by Frank Oz. Yoda's evil twin, if you will. His good-for-nothing brother-in-law.