**** MORE SPOILER WARNING ****
1. Young Flying Fox is an earlier story of Hu Fei. Reading XSFH, you'd know that Hu Fei is still unattached at that time.
2. He has some relationships in Young Flying Fox, including with Lingsu. I think he likes her basically like a younger sister, but it was more complicated than that.
3. I don't recollect it.
Again, XSFH is a very deceptive book. You don't realize that Hu Fei IS the protagonist until quite late in the book, and Jin Yong does it on purpose with his usual craftiness.
So, Hu Fei is the one faced with a choice to revenge his father at this point or to stop the fight and clarify the matter. After all the girl he's engaged to is the opponent's daughter and she deserves a chance.
About the snow etc, since when this little things kill wuxia fighters? Jumping into the ravine usually doesn't kill the wuxia fighters, even less such small danger such as unstable snow etc... (hehehe).