"What do you or your readers make of Jesus' references to 'the ruler of the world' - Satan as mentioned in John 14:30 and other places? These references leave me with the feeling that Jesus is in fear of Satan even though he states 'he has no power over me.' I hear about avoiding sin during Sunday homilies, but I hear little about avoiding Satan, as if he doesn't exist or no one seems to have a good grasp on who/what he is."
Jesus said his kingdom is not of this world, so saying that Satan rules this world yet "has no power over me" is like me saying that Raul Castro rules Cuba yet has no power over me.
As you say, this gets into the whole issue of who or what Satan is. I've held different views on this over the years, but now I essentially believe that Satan is a psychologically useful personification of the evil within us that pulls us away from God. Why useful? Because it's easier to resist something that is seen as an outside force than to wrestle with the darkness within yourself -- or even to admit that it exists.
The problem with externalizing this evil, though, is that it makes it all too easy to see it only in other people rather than wrestling with it in your own heart.
Evil is real. It is destructive. It is the opposite of love. It separates us from God and one another. How you picture it (personally, I love C.S. Lewis' depiction of Satanic plotting in "The Screwtape Letters") is far less important than whether you resist it.