Moira is wearing Riley's old hat band.
The tree when it fell was shown as swinging down on an arc knocking Alex backward. Since it was a heavy main branch (more like a trunk) it would have fallen straight down, not on an arc. As such, since he was standing up, it would have either hit him in the head or missed him completely.
Stevie never considered using a rope with her vehicle to pull the tree off of Alex. This is out of character for her as she has consistently been a strong-willed woman capable of independent thinking, especially during a crisis.