We took down the Christmas decorations today, but I left Chelsea's purple ribbon. It' been very enlightening reading WSers posts who have been following this case. Almost all of your ideas make great sense. I keep leaning on the idea that this POI knew her from before, even if she wasn't all that familiar with him. He may have used a ruse to get her in his car. The things that stand out, is that nobody seems to know him, and if that is true, and it's not somebody being protected by friends from BM's bash, then these things stand out.
That burglary at the gas station in Maybee, about 26 or more hours later. If it has anything to do with Chelsea Bruck going missing, could have been for gas money and supplies the POI may have needed to get far, because he didn't want to charge it? So could he have paid cash for gas around there a day or so later to get away? He may have hunkered down somewhere until then?
The possible connection to Julia's death, even if it was something that hadn't been planned, if it was the same person, and they had followed the families, then seeing Chelsea Bruck needing a ride may have been too great a temptation.
This does not seem to be the only time this POI may have been involved with something like this. If he is known to LE or not, there is so little information or indication of what happened to Chelsea Bruck that I think this person knew what they were doing. He may have had what he needed to in terms of knowledge, awareness, means, and motive to cover their tracks.