Occam's razor dictates that "Among competing hypotheses, the one with the fewest assumptions should be selected." Personally I believe you have summed up the entire incident as much as it need be summed up, without wild goose chasing and red herrings.
All the fancy stories built around the idea of a fantastical drug buying scenario just are not supported by any real facts. The smoke buddy key chain ? Well, its cute for one. Could be a gift - and she was dating the fella who lives in Colorado where marihuana is legal. It would be a natural tourist thing to do while you are there, like visiting Amsterdam. But to depict DS like some drug starved heroin addict, going way out of her way for a bag of weed ? That is off the track and unrealistic in this day and age, as well as not suiting her description.
The media mentions the MetLife security guard, and LE searched the Berkley house where that person lives. Am I wrong for assuming that this person would probably have a firearm ? A gun pointed in a persons face is all that need to occur in any abduction, without tangents like affairs, pregnancies or drug deals.
As for why IGA would put up a reward, it is just horrible PR to have a young woman snatched from your property. A simple face saving move perhaps, although I do not deny it's benevolence.
As for why MetLife would put up a reward, if there is any chance that another employee was involved and it ends as a homicide, they may be liable in a wrongful death suit. Again, I think both places offering rewards was a benevolent act, and it personally moved me greatly when I learned of their contributions.
Here is my theory at this point and my reasoning:
DS left for work, and the security guard or somebody else associated with that building saw her leaving, and followed her home.
I believe this person already knew where she lived and had planned his exit to some degree.
The Perp pulled up just as DS had parked and locked her Jeep door and before she headed into the building.
The Perp opened his passenger door, pointed a gun at DS and said "get in or I will shoot, do not scream"
DS got in the vehicle with the Perp.
The Perp drove the vehicle onto Halsted, turned on Grand River, and went straight onto the M5 entrance ramp.
The Perp drove the fastest route to the Berkley location, which was M5 to 696 to the 10 Mile Rd/Coolidge Rd exit.
DS's Jeep was left exactly where she parked it on Friday night, when she left her purse etc in the car, and took her keys to go in the apartment. Her phone was probably still in her pocket.
I dont believe she drove the Perp in the Jeep. It gets too complicated and required Perp to have help or take other transport to the MetLife office, any way you run that scenario - he is needing a ride to her office, or back from her apartment etc. Too complicated. The simple explanation also accounts for why her purse, ID and money were locked in the car.
I believe the Perp took her to the Berkley house because LE must have evidence that would allow search and seizure of property at that location.
I believe she was in his car because they took his car, and because it fits the simple explanation of events.
I do not believe Perp was in her Jeep, because I think he would have made the purse disappear because it being left behind was an immediate red flag.
The purse in the Jeep is also the reason no theory about her going with the Perp voluntarily for any reason is valid.
Like the rest of the normal people here, I just can not put myself into the mindset of a predator like this, yet we all know too many of them exist.
As for if DS knew the security guard, well sure she probably was an acquaintance. And that could be part of suckering her into a vulnerable position where a threat could be made to get her into a vehicle. But imagining romantic relationships is too much for me with no facts to support the idea.
Whoever lives at the Berkley house, they do not appear to be there currently. The driveway gate has been swinging open in the wind for days, and nobody has removed the MISSING flier stapled to the tree in front of the house. Looks abandoned.