Agree, OS is totally in Situation.
I'm not sure if I agree that the Drivers have to do with the family yelling at Kevin, banishing him, eating pizza, or even the ticket getting thrown in the trash.
How would any of those affect everyone and drive the OS?
Isn't that all just RS stuff in Mind? Maybe MC stuff too?
If I were to wager a guess at the drivers, I'd say the following:
OS = Being Home Alone during Xmas at the McAllister House.
Initial Story Driver: McCallister Family reveal their plans to leave the house unoccupied at Xmas --> Fake Cop Wet Bandit decides to make that house their primary target.
This is the major thing that affects everyone, right? Potential for the whole story rests on the family leaving, and the criminals invading the empty house. Kevin being there alone is the major problem. The benchmark would probably have something to do with the family (mom in particular) hitting one roadblock after the next to get home, so Kevin wouldn't be in danger, alone at home.
Act 1 Driver: Family miscounts heads, leave Kevin behind, Home Alone --> Family decides not to double-check before they leave/board the flight.
(This sets up Act 2: Kevin is now Home Alone and the Wet Bandits are poised to invade. Kevin and their house, and the neighborhood at large is in danger.)
Midpoint: The False Victory: Still Home Alone with bandits in pursuit, Kevin hosts a fake party at the house --> Wet Bandits decide not to pursue the house, figuring they got bad intel.
Act 3 Driver: Operating on their new intel, the Wet Bandits invade the McCallister home --> Still Home Alone, instead of telling an adult or any authority figures, Kevin decides to defend his home on his own.
Concluding Driver: Family comes home just in time for Xmas Day.
All the stuff after that with the family showing back up, reunion with the mom, neighbor reuniting with his son... all feels like RS, MC and IC stuff to me, not OS.