Do you mean, deliver a cut to someone in Chantilly? That's a possibility. He says he dropped off the $40k in the car in DC, but we know he's a, well, fibber. What's your thought?
I think he visited Chantilly to establish an explanation for why his DNA or other evidence may be found at the dojo. I think it is possible that SS was overtaken at the dojo and when it got dark, taken to his home in the trunk of his car, which is why they have now impounded the other three cars.
While Amy was at school picking up PS, DW put on the vest and knocked on the door. Vera would have been alone or just leaving.
JMO