It seems to me at this point the case is a waiting game. LE knows one (or maybe two) of the POIs are responsible for her disappearance, but they don't have enough hard evidence to make an arrest. They won't release what they know so as to have ammunition for interrogating whoever finally gets named.
Until they find the body or one of the POIs cracks/makes a mistake, this is a stalemate. No amount of guessing regarding the timeline in this forum will help because we don't know the real timeline, only LE does.
In the longer term, I think Mama and Papa Spierer are going to make a serious attack in civil court.
That's exactly what I also think. Your analysis makes sense.
I am also convinced that JW has nothing to do with it and it is silly for some to even suggest so. He was the one who reported LS missing to the police. People who are guilty dont go to the police as he did. He must feel terrible for her disappearance and it is unfortunate that he was even considered a POI (as all boyfriends/husbands do in cases of disappearance), but he is obviously unrelated to the whole thing. Otherwise, he would not have gone to the police or initiate the search, as he did