You can't have it both ways. Either free will or no omni-everything supernatural entity.
It rather depends how one defines "free will". As Schopenhauer pointed out, there are actually two different kinds of 'free will' - there is the idea that we are free to act as we choose to act (the common-sense definition), and there is the idea that our will itself is free from causality; that we can choose to act in any way we please, and that
our willing itself is not part of the causal nexus (this is
metaphysical free will). Metaphysical free will is a huge claim - since our free will, to be meaningful, must be an expression of our own inner nature, it is a claim that our own inner nature itself, our personality and our set of habits, values, &c are not determined by our environment and by our brain activity, but are acausal and spontaneously generate themselves. Needless to say, I don't believe in metaphysical free will for one second - it's just as much a flight of metaphysical fancy as believing in a transcendent, omniscient deity. We need therefore consider only the first definition of free will - the idea that we are free to act in accordance with our own inner nature; which is to say, in accordance with our personality, our values and our habits of thought. The point is that our own inner nature is itself part of the causal nexus, and is determined by our genetics, our environment, the books we have read, and so on and so forth. Our will is therefore itself
determined by the causal nexus, and is not
metaphysically free. And our actions are determined by our will. At no point, therefore, is the chain of causality broken. This means that an omniscient deity (assuming that one exists) could indeed predict ahead of time exactly what choices we will make in any given situation, and this is clearly not incompatible with the existence of human free will, since that 'free' will is itself determined by our own inner nature (otherwise it would not be
our free will, but merely random actions chosen by, say, flipping a coin), which itself is determined by our genetics, our upbringing, our environment, our situation and our brain activity at that moment. But even though our choices and actions would be predictable to an omniscient being, we still have 'free will', since our choices and actions are still an expression of own inner nature as it responds to a particular situation.
"Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies." - Marx (Groucho)