I beleive that some version of the third point holds. What might a plausible physical theory be? I dunno, I can guess its some quantum-gravitational thing, where the universe attempts to arrange itself in some consistent order. It mostly manages to do so (ergo, three (or more) spatial dimensions), but is left with some tangled knots that are not resolvable (ergo, low-dimensional leftover, i.e. time). The propogation of these unresolved knots into a self consitent state wwe perceive as the flow of time. The consistent past cannot be made unconsistent, which is why we cannot change history. The resolution in the future is fundamentally unknowable, even by the universe itself (for if it was, there'd be no need for time.) This is one metaphysical but plausible answer to the question of 'what is the physics of free will'?
The secondary question follows: If we've acknowledged that free will exists and has a basis in (a yet unknown) mathematical physics, then what other mental phenomena belong to this category (as opposed to mental phenomena that are 'merely psychological/memetic' in some traditional medical/neuroscientific/memetic sense)?
Its socially safe to argue that free will must exist and have some basis in a mathematical/physical reality. Its quite dangerous to argue that a mystical/transcendant experience uses the same physical mechanism to exhibit itself. In part, this is because medical experience with drugs has greatly devalued the experience of (e.g.) Zen, or the (e.g.) Christian mystical experience. There seem to be drugs known to the medical establishment that will induce experiences that are sufficiently similar to the mysitcal experience that skeptics like to handwave along the lines of 'ah so-n-so just has a chemical imbalance that can be treated with a good nights sleep, a proper diet and some good excercise'. That this may be missing the point is argued by Hameroff in his 'more neural than thou' debates. Assuming that there are structures in the brain that interact with the flow of time in the universe, then it shouldn't be surprising that drugs can act as sand in the machinery, leading the brain to perceive alternate realities.
The point here is this: rather than attempting to study how the physics of the flow of time allows for the existance of free will, maybe it would be more fruitful to pick some other, more tractable mystical state? (By which I mean to imply that the beleif in free will, and the perception that it exists is a certain kind of mystical state in itself. By attempting to touch it with rational means, it has a way of melting away: under a microscope, free will evaporates into into a nebulous philosophical je-ne-sais-quoi. But this is just like any mystical experience: it evaporates, and can't really be put into words (e.g. Zen).) Which mysitcal experiences are 'real', in that they touch the raw unfolding of the universe, and which are 'fake' in that they are explainable via disease or hormonal imbalances in the neural netowrk? Are there any 'real' mystical experiences, or is the humdrum daily life as close as we get to the inner workings of the universe?