Here's the problem with your entire premise. You are confusing God's "time" with our time. God sees everything as one NOW. He lives in the eternally present. The Scripture speaks in human terms - that God decrees before we existed. However, God is not subject to time, since He created it. Thus, God does not literally plan things on T minus day one of creation, then goes to sleep, wakes up, and then each day, consults His pre-planned chart of things to do today and ensure that it will happen! Thus, it is more accurate to say that God's plan are of the ultimate in fluidity, as they take everything done into account in His eternal PRESENT.
Since God sees yesterday, today, and tommorrow as ONE EVENT, His decrees ARE our actions! Thus, free will is not destroyed, nor is God's omnipotentence and foresight. I believe your mistake comes from applying time to God. Thus, you believe that our names cannot be blotted out. You think they are already written 6000 years/20 billion years ago - to God.
Regards
While God is not subjected to the laws of time, His creation and creatures are. The universe, the angels and man are all subject to time and will forever be subject to it. God works within the bounds of time but He is not bound to it and, make no mistake, neither is His creation if He so deems. There are two places in scripture that shows God physically altering time (one in Joshua and another in Isaiah). God can alter time just as He can change anything else but apart from these two incidences there is no indication that He is so inclined. When God sent an angel to Daniel, Satan withstood him for 21 days until Michael came to help (Dan 10). God works within the framework of time unless He doesn't want to. That's His business.
God is always one step ahead of everything in His created universe. Satan hindering angels, God incremental creation and the Book of Life all shows stop and start points. God is not bound by these but He works within this framework. Scriptures state the Book of Life was created and sealed BEFORE the foundation of worlds. I personally believe just that.