Hmm...
Your RDI says that JR was abusing JBR.
Someone was. I just happen to think it was JR because of a number of factors. So, yes.
She started to talk, so PR lost it and accidentally killed her.
Either that, or she was so angered by the "lies" that she flipped out, struck her, then realized what had happened. Either way, it was not an intentional killing. I happen to lean toward the former. So, in short, yes.
Then, to cover up chronic abuse, PR and JR staged a kidnap for ransom turned sexual assault and strangulation murder. Is this right?
Yes, essentially. I happen to think there were other reasons too, but that was the big one, for me.