Just taking this lime idea further, and bouncing off NL:
1. Is it correct that group B ( the body parts ) were found the day AFTER group A ( items of clothing, paraphernalia )? Perhaps they were not there until late that night? Suppose the finding of those articles had panicked him into removing the remains he'd planned to leave there? The lime theory would allow for this, as the more defleshed & peripheral parts (thin-skin parts like scalp, finger tips, & jaw) separate, fall out & scatter--especially in the dark, and even be further scattered of kicked around as he struggles with the tarp-wrapped, disintegrating body.
2.. She could have been murdered ON the blanket. Subdued for the drive--knocked out, drugged, or something else--but preferably no blood in the vehicle. Duct taped quiet and bound. Remember, Sunday could have given ample prep time--for finding the right hidden place to dig a girl-sized hole, place a waiting tarp in it, even stow a couple of large bags of lime... Unconscious or tied up -- fighting for her life and her child--he cold-blooded and also provoked. 20 wounds in the same spot. It sickens to think about all this. Grieves. Yet, it has to be examined. I want to know--would the full womb itself protect the mother from the stabs? As a barrier? Hence his grotesque stabbing repeating in a frenzy? Then, as he planned it, remove clothing, drag on blanket to tarp-lined depression, having lined it with ample lime. Next roll the body onto the bed of lime and cover thickly with the next bag and maybe another for good measure--the clothing having been removed to assure contact with the skin. Then, close up the tarp, sealing with the duct tape. That done, strip down and wash up. ...Why leave jeans, gloves, tape and her clothes? Didn't expect to be found, maybe. ...As was noted, it was the ping and only the ping that caused them to go to that site. And he was lazy (we heard) --so not apt to clean up his own mess.
3. Somewhere, I think she is in a large plastic bag. Maybe at the dump. I feel worst of all saying that. But, that would make sense, to my mind.
4. Referring to some talk earlier, about the grill and other car parts. AND Pua's (right?) making the connection between the robbery and the car part person--this house in Haiku where they found the grill, etc. this seems to be very important, and it's been largely dismissed. Girl once associated with SC gets robbed of jewelry & computers, tires also slashed--the stuff found months later, after the murder, at his house. But it sounds as if they only found out about the robbery because they had visited her house to investigate the SUV grill & other parts--then she reported the robbery AND the supposed perp--SC! Then the search of his house & finding the stolen items, proving his involvement with the house where the car parts were, right? What to make of all this?