Satan is a cop out. Either your god created Satan to take the fall or Satan exists as ANOTHER uncaused cause independent of God. How many of those are there? If Satan controls your god-created world, one of two things must be true - either your god allows it for his own purposes which is simply evil or your god is unable to take back his own creation and is not omnipotent.One simple thing you are overlooking in asking those questions about innocent children being murdered is this, The Bible and Jesus himself stated that Satan the Devil is the ruler of this disaster of a world.
1John 5:19-" We know we originate with God, but the whole world is lying in the power of the wicked one."
Jesus stated, "I will not speak with you much more, for the ruler of the world is coming, and he has no hold on me". John 14:30
Earlier at John 12:31 he said "Now there is a judging of this world; now the ruler of this world will be cast out".
So its pretty clear that even Jesus acknowledged that Satan was in control of the world at this present time. That is even more clear when Jesus was tempted in the wilderness by Satan, who offered Jesus all the kingdoms of the world in exchange for an act of worship. If Satan was not in control, he could not have offered Jesus those kingdoms.
Another factor to consider is the sinful human condition that we inherited from our first parents' wrong choice. Some of the things that happen are just "time and unexpected events overtake them all"( Ecclesiastes 9:11)
To blame God for any murderous act goes against His very being of being a God of Love.
James 1:13 says"When under trial, let no one say: "I am being tried by God." For with evil things God cannot be tried, not does he himself try anyone.
You earlier mentioned the account of Noah and the flood. The world that was destroyed was filled with violence and not with just people. It included a group of demon/human hybrid offspring who were violent and destructive. So for God to say the earth was "ruined" in His sight is pretty telling. It must have been REALLY bad.
Noah and his family were spared because the Bible says "he walked with the true God".
And that last bit is just woo-woo.