Kylo most likely isn't a Sith and even if he is the rule of two would have died with Palpatine and Vader. Besides the rule of two was just something created by Bane because he was scared of all them up and comers. Its easier to watch one greedy power hungry apprentice than 20.

Jury is still out on if Finn will be force sensitive or not. Secondly, Storm Troopers haven't been clones in quite some time, remember they had accelerated aging that pretty much gave them short life spans. Once they began to die out they were replaced with regular ol' humans.