thank you for asking all the questions I want to ask myself!
I'll try to come up with answers. I've either tried to be as funny/crazy as possible or just tell you what I honestly think.

1. Fuji's probably too scary if he has his eyes open all the time. (if you're familiar with his twisted side... which I love so much)
2. Maybe his genes just react to rackets.
3. He probably is one.
4. He's too good at tennis, the godliness takes away his smiles
5. Healthy hobby. (sarcasm totally not intended, no not at all)
6. Maybe he has a superpower that gives him as much force during games as how much he's eaten recently. Explains his dunk smash, jack knife, and so on. Explains Momo.
7. Too many people call him a snake. (momo did about 89% of that, Inui tells me)
8. The author calls it egg hair. Fanfics make fun of it. His hair used to be normal (in the anime, when he is a freshman). Honestly, I have no idea.
9. Ponta is his essence of life. Can't he just love me?