Free choices aren't random, they aren't free from being caused but rather they are caused in the right way based on the beliefs and desires of the agent. A choice is made freely when the agent could have chosen otherwise if the agents beliefs and desires were different.
Metaphysical means "beyond physical", I don't believe that he said anything that is anything but based in the physical reality in his claims.
Does he specify why this means we have free will? The brain doesn't exist in a vacuum.
Because a toilet has mechanisms to control how much water it stores awaiting to be used to flush, could we then argue that the toilet has free will? I see this "proof of free will" as a neural (whatever its called) "water level in toilet controller", and not free will. I don't see how he drew his conclusion.
That area of the brain (the medial frontal cortex) controls activity, so that the system we call the human body can function properly.
The brain is influenced by what goes on in its enviroment. Unless he says why what he says is proof of free will, I remain unconvinced.