In fact, only about 10% of the human species can be considered to be genuinely 'sinful'. Most of us, including my own non believing self, are essentially good people, whose sins are trivial.
You are contradicting yourself. In fact, that is a benchmark for contradiction.
I am not a big fan of the word "sin" and the word can be substituted for many things and they would signify the same thing. However, if we were to use it then there are different levels of sin. One can be simply telling a lie.
And babies are born innocent. Sure, they may later develop into Dr. Crippen clones, but at birth they lack sin. Millions of these innocents die in great pain within a year of being born, from disease, famine, or natural disaster. All of these are "Acts of God." You cannot justify that as the act of a good God. If God exists, and is all powerful, then he must be evil.
Of course babies are born innocent but they also have never done anything at all. They may die from great pain but they were also born from what some would consider great pain.
I dont understand your logic in that last sentence either. If a large tree branch falls and hits someone on the head and the are (obviously) in great pain and die hours later what does that mean? Surely not that the branch was evil.
Also, you need to remember that pain serves a purpose. Mainly telling the person in pain that there is a problem so it isnt something we can just eliminate.