That whole argument of "free will existence" is kinda pointless. You can't prove neither existence, nor non-existence of something, while being inside that universe where that something is controlled by definition from "outside".
That's actually quite the same as arguing for or against God's (The One, Source, Allah, etc) existence.
It's just, if I were the God, it would be much more interesting to have certain rules for certain universe and then allow rules to play out themselves, then maybe incarnate as many observers, thus creating and observing element of randomness, eternal change and surprise.
On the other hand, one can argue that God exists outside of time and thus, everything is laid out infront of divine eyes, all at the same time, as there is no time in God's realm.
Don't know, maybe God allows themselves experience time while incarnating observers in material universe.
And forgot to add: and if there is no God, then you would require a computer much bigger than size of a Universe to compute the Universe and calculate your next non-free-will step, so good luck building it, iirc this is a mathematically proven fact.
There is also another type of "no free will" camp, championed by Sapolski, he's making some very straightforward argument.
It's that your starting condition and growing conditions predefine a lot of things in you, even if you think you have chosen them for yourselves.
This is another realm of "free will" discussion and is more of a human hardware/biological discussion, rather than proper philosophical one.
Disclaimer: all above is IMHO and I would like to hear some interesting thoughts for and against my points.
Blind_Goat
It was an interesting read, thank you.