Note: when I threw out 10 years as a plea number, that's not supposed to be a real guess or spec. It's just an example of how pleas on murder can end up with an undesirable (for us) reduction.
I have no idea what they would offer SC, not a clue.
I have read that the enhanced circumstances on second degree is tough to actually get applied, in some postings by Brooke. I honestly don't think they have proved the torture element. Rivera is going to need to really sell his facts and a strong theory.
As of now, as we see in this forum, reasonable people can form a variety of takes on what, where, and how it went down, at what point she was killed. What he did to her after death is grotesque and unspeakable in my book, but it doesn't count in this state to enhance the penalty.