Can you please help me with the following?

1) The nose of the boat hit the first one (of the rocks) head-on, popping up, flipping the boat over. Where is the subject in this sentence? Who 'flips' the boat? What does it mean head-on (front part, tip of the boat?)

2)She ran full force toward the picture window, tucking her head as she broke out the glass. (Did she tuck her head in her shoulders and break the glass with her body?)

3)To think that this had al started when Jack attacked her made Sara's stomach turn. (As when you are sick or nervous?)

Thank you
1-- The subject is nose. Head-on = head first and directly; yes, front part first.

2-- That is about how I envision it, Antonia.

3-- Yes, upset in some way; here, I think it suggests repulsion.
Thank you Mister Micawber.