I might also add, that if man does not possess free will, then he cannot sin.
Therefore your god is punishing man for what he cannot help but be, a bit like me kicking a dog for having four legs.
Well, what is "free will" anyway? My impression from the way people use the term is that it is a deviation from a pre-destined fate or destiny.
If the universe follows the laws of physics and chemistry and these laws are mathematical and logical in nature, then the universe follows a deterministic course of events. That would mean that deviation from a pre-destined fate or destiny is impossible.
Of course, according to the latest theories, we also have a probabilistic universe. It makes it less deterministic, but at the same time you can't refute the fact that the universe is completely filled with mindless entities with no intelligence, let alone the ability to make choices.
How could free will exist in such a universe?
I would suggest that it depends on your definition of free will.
Consider for example, the notion of human rights. It is the idea that due to the level of sentience of human beings, they deserve to be treated with a certain level of dignity. It has much to do with "free will."
We may well be programmed entities, composed of millions and billions of mindless entities. These mindless entities function within the bounds of predictability at the microscopic level, but on a macroscopic level, they work together to show intelligence, sentience and rational decision-making. If free will is defined as intelligent behaviour that deviates from the bounds of predictability, then we possess free will.
But I realise that the issue with "free will" isn't about intelligence or sentience. It's about God being able to predict the destiny of each and every individual. It means we should reject all favours from God because everything God does is a manipulation. Ultimately, nobody deserves anything because everybody is made of mindless components that operate within the bounds of predictability on a microscopic level and God already knows what's going to happen anyway.
But couldn't God choose not to use that ability for ethical reasons? For example, it's commonly believed that God is a mind reader. But God can choose not to read your mind without your consent. Maybe you have to ask God to read your mind. Likewise, you may have to ask God to be calculative.
God may not actually know what's going to happen. He may have chosen not to know. God doesn't have to know if you don't want Him to know. You can ask God to stop reading your mind. You can ask God to stop trying to predict your future. You can tell God to stay out of your life. I am assuming that all these are valid and legitimate requests.