To understand why the benevolent God can allow all these terrible things to happen, you have to understand what happened for things to be this way. God created all people to live a perfect life by themselves, but since Adam and Eve disobeyed one of his orders, he punished him and those that came from him.
What he wants most is for his creation to love him, despite the chaos that has ensued by man and Satan. Even though he has omnipotence, remember that we were done of his image. We are not as far apart as people like to think.
Imagine we are talking about natural disasters. God does not cause natural disasters, he is not using them to inflict punishment. These natural occurrences have been going on since Creation. The Bible predicted those disasters (Lucas 21:10,11), but it did not mean God or Jesus or Satan were responsible for them, much like how a meteorologist is not responsible for the weather.
It is implied that we are responsible for problems resulting from those disasters, for not listening to warnings (Proverbs 22:3). Many things the Bible teaches is to be pay attention and heed warnings, so he does in fact help us with those problems. A person that stays behind on his house during a huge hurricane is going to have it tougher than one who evacuates.
But what if he had no choice? It is not God's fault, it's man's fault. While other countries enjoy great prosperity and order, third world countries do not, due to corruption. Even if the country was in an nonstrategic place for resources, trade would fix that, if it weren't for the inherent problems with politicians wanting stuff from each other. God is not going to intervene with human governments, because it is not his. You want to rule yourself, you are by yourself.
But does that mean God is allowing it to happen just 'to strengthen us'? That he is mean and evil and a jerk? The same thing happened to him! He sent his son to Earth to help and educate the Earth from Satan, as a sign of love (John 3:16), and we killed him. Those terrible things that happen to us are not to strengthen us, or to understand what others go through. He is just as sad of it happening to us as we are, which is why he publicly showed his power in ancient times, inspired the Bible, and sent his son in the first place.
But why he doesn't he still show his power now? I'm sure that would shut up all the Atheists! Because he tasked his son, and he tasked his disciples to spread the knowledge of his power, so that he wouldn't have to show it the hard way. He still listens to us, and gives opportunities for us for him to help us, but we have to realize it ourselves. It won't be worth anything if he does it all for us, as previous events showed. He wants you to believe it for yourself, because it might be taken for granted, and lead to another Adam and Eve event.
But if Satan caused everything, why didn't God stop him? That's not what a loving parent does! This is based on an opinion of what a loving parent is. Is the loving parent a good parent? A 'loving' parent would give his kid anything he wants, like give him all the candy and chocolate he wanted over real food, or buy him anything he wanted, no matter the price. But since the high amount of sugar would lead to disease, and high amount of spending would lead to financial problems, this would mean a very bad parent, even if he/she was well meaning.
But God is all-knowing, and knows the consequences. Because he loves us, he does not allow everything to be as we wanted it to be, even if it makes us angry or sad or devastated. He purged Satan from heaven, and now he is running amok on Earth. He trusts us to make the right decisions and not fall for his traps, no matter how good they are, because they will be good. (Ephesians 6:13)