To begin with, God plants a garden to the east of his location (Genesis 2:8), then when man is expelled he is sent further eastwards (Genesis 3:24), and finally when Cain is expelled even further, he goes into Nod which to is yet further eastwards (Genesis 4:16).
To begin with, it doesn't say that the garden was planted to the east of God's location. It just says it was planted in the east, which could have easily meant that it was east of the writer's location.
Secondly, the expulsion of Cain is not said to be even further east than the expulsion of Adam and Eve. Both are said to be east of Eden, and it doesn't really say which is further east.
No getting away from Him eh? Thank you LordWell if you go east or west far enough you eventually end up coming from the opposite direction. So perhaps it's symbolic of separation from God like you said, but even as we continue to go further 'east', we will eventually wrap around the sphere and come from the west, and find God again (Revelation 7:9-17).