We are not in the past though. For us it is the present, but, you seem to be saying, it is the past for God because it already happened for him. This however is false. God knows because he is observing. Every moment past present future is the present to God. In fact, from after time ends God is still observing every moment. He really has no future, he is a present God.
Nor does the fact that we choose one way, that what we will choose is already known, and that once we choose we cannot change our choice undermine free-will. That we will choose one way and not both ways or a number of ways is obvious as is that we cannot change that choice once we have made it- not to say, however, that once we choose to say become an athiest we cannot change that choice and be a buddhist or something else. Regarding the other point: it is by no means true that simply because an entity is aware of a future event or choice that they caused it. This is a non-sequitur. To know is not to cause.