1) different for every person
2) different for every person
Average hairloss per day is estimated differently by everyone, from 50-100 to 75-150, to 100-200. It really depends who you talk to. If you don't have male pattern baldness, the more you lose, the more you grow back following it. That's really all there is to it.
Edit: And you may grow back all the hair you lose while you have male pattern baldness, but it'll come back finer and shorter, and die faster and faster and faster, such is the cycle of male pattern baldness.