Well, again, thats a lot of questions. First off, God did create the world and humans perfect. Without disease and cancer. But in this perfect world, he gave humans a free will. The fist human, Adam, didn't even know what evil was untill it was presented to him. Unfortunately, he chose evil instead of good, and thats when sin entered the world. We live in a fallen world full of sickness and disease because of that. Sure, God could take it all away, but he would have to take away our free will. He wants his creation to be able to love him back, but to do that we have to have the choice to be able to do that. Or to hate him. Without freewill, there would be no choice, and we'd all be robots doing whatever he wants. So, for example, Jesus tells us to "love one another". We'll, if the whole world would seriously do that, we would eliminate half of the evil things in the world. There'd be no starving kids, heck, I believe we already know the cures for cancer, so there'd be no kids dying of cancer. But because of our fallen nature and our selfishness, we'd rather get rich and start wars and not care for one another. So that's a start for you.
One more thing I like to say, is that God is eternal. No beginning, no end. That's hard for our finite human minds to grasp. He exists outside of our concept of space and time. If we could fully comprehend him, he wouldn't be God. So to say that God is evil or wrong to do whatever he wants with his own creation, is just naive. But he met us on our own level when he came down as Jesus. Not only did he give us an example of how to live a perfect life, he fixed our problem by taking our sins away and giving us eternal life. He offers us this free gift. But, just as if I were to give you something, you wouldn't have it until you actually reached out and grabbed ahold of it. So believe that He is and grab onto Him. And that's the first step to understanding Him.