I don't mind that the producers didn't provide all the awnswers in concrete terms. It gives me the chance to come to my conclusions. Isn't one of the themes of the show all about making your own choices?
Why was Walt special and why did the Others want him? Well the Others could tell that he had psychic powers and it's always good to have a psychic on your side. Plus they had indoor plumbing and the Lostie didn't so they were looking for Walt in that regard. And don't bring up the toilet in the hatch. You think sharing one bathroom with your two roomates is bad, try sharing it with 40 stinky survivors.
Why couldn't women have babies on the island? That was Jacobs thing. Part of it was crowd control. Part of it was that he didn't want children to have to grow up in a harsh environment. He didn't want children robbed of their innocence. Though sometimes he made exceptions for various reasons, i.e. the mothers were candidates, or maybe he just felt like changing things up. He was kind of fickle like that.
What was the deal with the numbers? They were just there to reinforce the notion that some people/things are meant to be together. The Losties were always crossing paths much like the numbers. The numbers wer ealso an extention of the light/dark, life/death theme epitomized by the glowing cave. The numbers bring good fortune and great harm just like the glowing cave. They take life and they give live. That's why Jacob assigned the numbers to the candidates. The Losties represented life, and death. They gave their lives and they took lives. They lived life and created life.
Where did the Dharma food drop from season 2 come from if the Island Dharma folk were all dead? The Others had an inside man at Dharma HQ back in the States hooking them up.