They are directed by a chain of cause/effect at the micro-level that began whenever the Universe began (if it did) and will end with the death of the universe.
That is a comforting feeling for some, but it doesn't seem a justified assumption.
Cause/effect occurs at the micro-level as well.
The unpredictability you refer to is due to the probability function of the effects of each cause. E.g. a single cause might have 20% chance of 5 separate effects. But this does not negate cause/effect.
Which is why two identical set-ups might have multiple outcomes.
But this is still predictable.
All I can say is I held this opinion to begin with but several physicists who understand quantum physics have explained to me that this just isn't how it works and the evidence that this is not how it works is very well established.
I understand this is disagreeable to some people, even other physicists, but I have to go with the current preponderence of the evidence.
I regret I don't have the math to discuss this directly, perhaps there are physicists hanging about who can do so in the physics threads.
If you knew everything about everything at one specific time interval then you could predict, within the realms of probability, the next moment.
The speed of light makes it impossible to know everything at one specific time interval. There is an envelope of Cdt which will effect the next moment but is further than you can know about.
The "will" you exerted to make what you saw as a choice was nothing more than the culmination of a massively complex chain of cause and effect up to the moment of "choice".
So you claim, but the evidence fails to pan out that way.
And if you hold that free-will / choice exists then please detail how the force/thing interacts with the chain of dominoes, without it, too, being part of another such chain?
Choosing is not a chain of dominoes. It is the complex interaction of billions of living organisms with trillions of interconnections which have both standing patterns of activity, self reference, traces of previous experience, attention, awareness, and choice.
Just like formal logic cannot handle the self reference in the liar's paradox, your formal causality cannot handle free will. The doesn't mean there is not free will. It means your system of explaning behavior in not sufficient to the task.