1. When a soul "dies" in soul society, they are reborn in the "real" world, correct?
2. What about people in the "real" world who already have both forms (Like Ichigo), what would happen if his shinigami form died, or his human form?
3. Do family ties apply after a soul dies in the real world?
How about if a soul dies in soul society?
4. Rukia is 140-150 years old, therefore it can be assumed that dying in soul society from old age is pretty hard.
Yet, the material world's population is getting steadily larger.
Where are all these extra souls coming from, if there is a balance?
Furthermore, you have a LOT of souls each year becoming hollows or being eaten by hollows.
It doesn't quite work out.