There is no such thing as belly button dandfruff, you probably just need to clean the inside of your belly button.
Clean it
you cant
No
Clean it out
Yes.
Yes. You could get a scratch in your belly button. Your belly button could get infected. Your belly button could bleed. If your belly button get infected you have to clean it with hydrogen peroxide rubbing alcohol iodine or antiseptic cream. If it doesn't heal after a week you have to see a doctor at the clinic or hospital.
With a Q-Tip.
Perhaps you don't clean it out regularly?
It grows on your belly button because u don't clean it well and u are born naturally, this is a major disease. You can get major lice so wash your belly button with toilet pee.
This page includes step by step directions on how to clean your navel. (http://www.wikihow.com/Clean-Your-Belly-Button)
At a clean and reputable tattoo and piercing studio.