The fact that people can still make choices without someone trying to actively make them fall into a trap, or the fact that if you love people, you don't try to mislead them ?
God doesn't mislead anyone.
He merely allows Satan to exist, who therefore can tempt humanity. God tries to show humanity the path, but he will not force anyone to take it. Satan is stronger on Earth because of all the deals and pleasures he can give you, but it is short-term; God's power is beyond the mortal plane, with eternal bliss being his reward. You are likely to endure much hardship in life, but just as savings for retirement reward you, "investments" in God reward you far more than any short fix from the Devil ever could.
God's love includes even the Devil it may seem - just as we humans punish murderers, many don't go so far as to advocate destroying them, only locking them up. God therefore lets him live. God's love for us extends to how he tries and tries to get us to follow the right way... but at the same time, that love gives him a dilemma: he must allow us to retain our free will as well.
To kill the Devil, or to strip us of our free will, would violate his love. He locks Satan up because he needs help, and it's the best God can do without killing one of his own children. As for why God allows Satan's influence to escape... I imagine it goes back to him providing choices for us.
You, again, completely miss the point. If God created life and the rest, he's the one who created the need for lifeforms to prey on each others, to kills each others and the like. Why a benevolent God would requires his creations to murder and eat each others, rather than getting their energy purely from the sun and minerals ?
Now this I have no idea on. But assuming Creationism didn't happen, except the first forms of life, then he is not to blame: evolution is. Evolution transformed the primitive lifeforms into predatorial beasts. Perhaps God's respect for free will extended to even the natural processes.
As I already mentioned, G_d gave authority to man, so how did it transfer to the devil/satan?
God gave us freedom of action and thought. At the same time, he allows Satan to influence us. Because humans are so prone to this temptation, Satan, by extension, "rules" the world.
While the Bible does indicate in several places that the devil/satan has autority over this world, I tend to find most Christians get upset when its mentioned. They seem to believe G_d and/or Jesus rules this world. This is just a personal observation though.
People do selectively choose which passages to follow from my personal observation.
Though it would make the most sense: sin is associated with mortal life, and it is Satan's influence. Satan "ruling" the mortal plane, through his influence on humanity, therefore, is perfectly logical. But he is a regent who rules at the discretion of his King - God. God could toast him at any time.