1.
If the area where the train track switches is a open field(if I can see the group of 5 and the1 person I should be able to see this as well) I'd pull the switch halfway to derail the train. after all the train isn't said to be a passenger train and the conductor and crew would half a higher chance of living then the people tied to the tracks.

2.
I'd go untie the people
3.
I'd go untie the people