I also agree that Kylo was lying to Rey when he said her parents were nobodies. It doesn't add up, and the way he played it it looked like he was lying. My main hope is that Rian Johnson wasn't just drawing the head of a body that JJ Abrams started, that there's cohesion to the story to be revealed in ep 9.

I have a theory about what Kylo was getting at when he dreamed of smashing the New Order and the resistance, and starting a co-thrown with Rey, although it's a bit of a stretch and it requires going way back in time. Consider that Yoda was looking for the person who was prophesied to restore balance to the Force. He saw in Anakin that potential person. Anakin goes dark, and Luke is now the hope to restore balance. However, it's actually Vader (Anakin) who kills the Emperor, so he was the chosen one after all, right? Maybe.

Fast forward to The Last Jedi. Luke's training of Rey focuses completely on balance: day/night, life/death, light side/dark side, etc. And Rey sees and almost embraces the dark side, even though we don't get the feeling she wants to be evil. Perhaps the message is that the Jedi, by only focusing on the light side of the Force, aren't actually encouraging balance. The light invites the dark, so that as long as their are Jedi, there will always be Sith, and vice versa. So here's where Kylo comes back. He recognizes this problem with the Jedi/Sith duality, and seeks to move past it. He isn't totally evil like Darth Sidious and his ilk, and obviously isn't all good like Yoda's trainees. He may be more dark than light, and Rey is more light than dark, but they're both a mix. He thinks that together, they can actually bring true balance back to the Force, and rule as benevolent despots.

This theory is a stretch, but it sort of explains why the peace that the rebellion secured in Return of the Jedi was so short lived (because it couldn't have been more than like 10-15 years based on how built up the New Order is by now, 30 years on). The Jedi were ascendant again, so of course the Sith were going to rise up; the Force almost guarantees this. Both must be killed to kill either. Perhaps Yoda's prophesy has yet to be fulfilled, and Kylo and Rey are the 'true' restorer's of balance. (I put 'true' in quotes, because obviously Disney is never going to let the saga be finished.) I have a lot of other thoughts, but that's the only partially original one.