The anger issues are fun thing to look at, his anger seems to center about Rey, what if she was a child to be trained by Luke (Likely Luke's daughter, but I think she might be Leia and Han's daughter as this would create the best story) and Ren decided against killing her with the rest so he take her to Jakku. Now let's get to the present, what if the reason Ren is so mad is because her being around is creating more inner conflict in him, now say Rey is Ren's sister, Ren is now facing a major conflict, he his Rey so he didn't have to kill her, but she's exposed herself, Snoke knows about her now, he has to or Snoke will destroy him, now the struggles between right and wrong, light and dark are at an all time high in Kyle Ren.

He is conflicted (There is still good in him) that's the big difference