Whether you call it foreknowledge or forethought it does not equate to cause.
Neither does speech equate to cause . . . except when God speaks.
You are trying to made an idea equal to an action.
Thoughts are actions. ...and bringing into captivity every thought to the obedience of Christ...
God desires that all should come to repentance,
I'm certain that the "us-ward" qualification has been explained to you countless times. There are those passages that are difficult, but this one isn't one of those. This one is so simple and clear only silver-haired anti-Cal curmudgeons could be too stubborn to yield.
Moving on...
that is forethought. But we know that not all do repent, why not if your premise were true?
See above.
But if your premise were true then God could in fact be charged with evil.
If God says he creates evil and darkness, Isaiah 45:7, meaning that he sends and rules the evil, yet holds that He is not the author of the evil, then who is Silverhair to argue with that? What knowledge does Silverhair possess by which he judges God?
So Paul says that one vessel is created to hold treasure, another is created to hold garbage. Pharaoh was raise up for the specific purpose of attempting to withstand God and to be destroyed.
And when Paul anticipated the carnal objections, like the ones Silverhair makes, to his exposition of God's sovereignty, He said, Who art thou, O man, that repliest
against God? You don't that's a good rebuttal, but that's not because it's a weak one, it's because you're not humble enough to consider it.
Did God foreknow that Satan would sin, of course. So if forethought equals cause then He caused Satan to sin and also all the sins the man would commit.
The Scriptures are completely silent about the world of angels and how evil entered in. (No, the Devil was never known as Lucifer.)
This we know, the evil that entered in serves God's eternal purposes. It's revealed to us that the Son would would have a work to do, and that even 'before' the beginning, that work would be to offer His body as a sacrifice for sin, and by that work earn a Name above all names in all existence. Without that work, He would not be worthy of that Name, nor of the worship due it.
There was never any alternative. It could never be any other way.
So...enough of this presumptuousness about the world of angels. As far as this world is concerned, which is the only world we've been given some revelation concerning, God determined that Adam would fall and sell out his progeny to sin. And He did this for the sake of His Son, Jesus Christ, Who came to do the Father's will, and that was to save His people from their sins, and bring many sons to glory.
If God's council is the cause of Satan sinning and thus Adam doing the same, no free will involved, then the responsibility for sin falls back to God as neither Satan or Adam could do other than God determined that they do.
In the end of the matter, in the New Heaven and the New Earth, there will be no 'ability' for anyone to sin, as you put it. So what what has become of your beloved 'free will.'?
If free will makes one's choice true love, is God now unjust to take it away?
Your man-made religion lands the responsibility for sin right back at the feet of God. If man has no free will but can only do as God has decreed there is no other option.
petitio principii