I've edited the material below to preserve anonymity and to make the discussion more concise. Sean K., maybe this material will be helpful to you.
God could make a human with a non-material mind, then fully determine that mind (theological determinism). Dualism doesn't automatically make the problem of free will go away, and it [actually] raises a new problem of agent-causation. How does an immaterial will bring about action in conjunction with all of the physical factors that exert causal influence on us? That question is not easily answered with the tools of science or philosophy. See Watson, Gary (editor). Free will. Oxford: Oxford Univ. Press, 2003. Flanagan, Owen J. The problem of the soul: two visions of mind and how to reconcile them. New York: Basic Books, 2002.
Here is where I'll broach the problem of overdetermination again. I'm not that comfortable saying "I am my brain" or "free will does not exist." It just seems that higher-level processes of the brain could explain free will and other conscious states. Conversely, I'm curious as to why you'd say that we need dualism to explain Alzheimer, addiction, hormones (etc.)? Could we not explain all of these phenomena by appealing to neurobiological processes? And if a physical cause is able to explain an effect, then why propose another cause for the effect (i.e., the problem of overdetermination)?
Addendum: On that last point, to illustrate, if pain can be explained adequately by natural factors and it's made better through analgesics, then why propose a supernatural factor to account for pain? Or if psychosis explains why a person hears voices, why claim that the person must be demon-possessed? If water can be explained by H20, why say that there must be something else that makes water, water?