God did not cast them out of the Garden. They distanced themselves from God when they sinned. This distancing is the natural result of sin. Nobody can come into the presence of God without holiness. We see how Adam and Eve hide themselves behind the bushes. We see them trying to cover themselves with leaves. Thats what sin does to us. It distances us from the presence of God.
Sin is not an act but a condition. The condition where man looses his capacity to know, love and serve God, and also his neighbour. The acts we commit are the fruit of this condition.
Are we not then, confessing only the fruits and not the condition itself!
We also see how God covers Adam and Eve with animal skin. We can assume that, an animal had to give up its life to cover them. In the act, God also covers them with the blood of the animal. This is probably how Cain learned the kind of sacrifice that would make him righteous before God.
God did not intent man to labour or suffer pain. Labour in the field and labour in child birth are also the direct effects of the original sin.
God the father sent His only son to save us from sin and the suffering it brought us. Through baptism God removes the effects of the original sin, and sets us free. The liberation nevertheless is experienced only when we apply the grace received in real life. This means we are set free only when we live according to the word of God/Spirit.
We should not blame God but ourselves for the cruelty, suffering and disasters we see in the world. But God in His mercy has turned even these suffering for our own good. The innocent sufferings of our brothers and sisters in many parts of the world causes God to pour out his graces abundantly. That is why it is said "But where sin increased, grace increased all the more. Rom 5:20".
The suffering will cease and peace will be established when all of humanity believe in Jesus Christ and order their lives according to His word. Because man cannot heal himself nor can he save himself.