Not sure I follow or agree with this. That you are a creation of something that knows what you are doing (to remove time from the equation) and determined or is determining that action through creation still seems to hold does it not?
I believe you are making a third assumption: God created a deterministic universe.
I don’t believe so. If god could create something that could act in way could couldn’t predict then is god really omniscient? Moreover – are you familiar with the problem of random number generation in computing?
I ascribe to MoonWater's description of omniscience:
Omniscience only necessarily includes knowledge of everything that can be known. My personal favorite example: Does God know the gestation time of unicorns?
In other words, does omniscience require that God know every imaginary, non-existent thing? The future is one of those things that does not exist; thus, omniscience does not necessarily "need" to know it. In these sorts of debates, I see "knowledge of the future" as something separate from omniscience. Unless, of course, the future
does exist, and then, as Wandered Off noted, it is not omniscience that causes free-will's demise; it is the construct of the universe that allows the future to exist (or to be predicted with 100% certainty) that causes free-will to poof into nothingness.
I am not familiar with the problem of random number generation in computing, however, I would assume that an omnipotent being would be able to figure a way to incooporate randomness into his creation (particularly if free-will is a characteristic he wants to bestow on said creation.)