"Satan's Domain"

"He cast upon them the fierceness of his anger, wrath, and indignation, and trouble, by sending evil angels among them." (Psalms 78:49) Well, let's just say it wasn't my first choice, I woke up thinking, 'Makin' Satan,' but could not bring myself to using it. I have long wondered where Satan came into existence, and how it is that he has so much power to be so destructive. Obviously it was pride; being made to contain such beauty and leading worship in heaven, could be something that makes one prideful. But this is an angel we are talking about; and not just any angel, but one that had position and a purpose. I say where because I think I known why, and it's not for the reason I just explained; but where is the part that I struggle with, because it can be so controversial of a topic to bring up. I know how this world became his kingdom; a kingdom that once was given to Adam, who gave it over to Satan by doing the one thing that God warned him not to do. At which time, we are meant to believe, that this world became 'fallen' and death began to take a place in the life of mankind. That one tree within the garden, that man was to not eat of, was called, "The tree of the knowledge of good and evil." Interesting to think about, but why mention 'good' and not just call it the "The tree of the knowledge of evil?" Good was something God used in creation, saying, "And God saw that it was good." But here is the thing that continues to blow my mind, in the God said, "Behold, the man is become as one of us, to know good and evil." (Genesis 3:22) With God, all things are good, there is no evil within Him. (1 John 1:5) So then, where did the evil that existed go? If there was knowledge of evil, it needed to have an original existence, right? There are a couple of questions that I have for God when I get to heaven. Then again, I think that all of our questions will be answered once we get there, because it will be 100% Light. So, in the meantime, we must understand real evil to be unrepentant sin, which is Satan's domain and why hell was created for him and his angels. Those that do not repent and receive God's offer of salvation will be joining him there for all eternity; ouch, that's a domain I want nothing to do with...
"This is the message we heard from Jesus and now declare to you: God is light, and there is no darkness in him at all. So we are lying if we say we have fellowship with God but we go on living in spiritual darkness; we are not practicing the truth. But if we are living in the light, as God is in the light, then we have fellowship with each other, and the blood of Jesus, his Son, cleanses us from all sin. If we claim we have no sin, we are only fooling ourselves and not living in the truth. But if we confess our sins to him, he is faithful and just to forgive us our sins and to cleanse us from all wickedness. If we claim we have not sinned, we are calling God a liar and showing that his word has no place in our hearts." (1 John 1:5-10) NLT