Frankly, I don't see you arguing that our decisions are not at least influenced; and if they are influenced, then to some degree, they are caused.
But, if the soul is not in some way materialistic, then it is unrelated to freewill, because the whole matter of freewill deals of material results: those things caused by our decisions.
And, if Free will has no causality, it does not exist, except in God alone.
My contention is not only that all things which God plans will be fulfilled, but that "all things, whatsoever shall come to pass" do so by God's plan. Therefore, whatever else 'freewill' may imply, it is necessarily bound by and defined by God's plan concerning it. Freewill logically cannot operate independently of God's plan. It is for this reason that many Calvinists claim there is no such thing as freewill.
To repeat: logically, if God is the only first cause, (which is definitive —i.e. "first cause" by definition logically demands singularity), then all other things result from his creating. If he created what he knew would result in a thing happening, he thus caused that thing to happen. Thus, if he knew all things, he, being the only Creator, caused all things.
I bring up 'chance', because, except for First Cause, nothing is uncaused. Since you claim freewill, and claim it by definition is causeless, the only alternative I can see is that you believe freewill's decisions happen by chance, since I can't imagine you would claim some truly altogether-spontaneous co-existence of mere creatures with God.
---------------------------------------
But allow me to go on a bit, here —I will try to describe some of the arguments (or should I call them simply, assertions?) I hear:
One is that by definition freewill is causeless, and that, by God's design, or that God has caused it to be causeless. They say that it is a gift of God to all mankind. Yet, they cannot see how that is self-contradictory.
Another takes the form of this quote, "It is the most sovereign thing God can do, to give up some of his sovereignty." And the one who said that, and many who heard it or think it, see no logical self-contradiction there. The delight in whatever seems counter-intuitive, particularly if it sounds poetic, apparently overrides rationality, for some people.
Maybe the best way I can describe this third, is the notion that God's sovereignty only rides herd on events within time. According to some, God's plans are only the end result, and not how to get there. This God, then, apparently must fly by the seat of his pants, and because he is all-wise and all-capable, he can figure out how to arrange things to the best end. Perhaps by this, they mean he recalibrates our reactions to life's circumstances? I don't know. The actual way this works is short of examples, though they claim all events demonstrate it. Some even claim that his original plans are sometimes defeated and he must settle for a contingent possibility.
Meanwhile, that third, and all others, continue to ignore the obvious, that if God knew what was going to result from his creation, but created anyway, then he purposely destined it to happen. And no, this does not mean he created sin, as it has been shown previously; God did not create my rebellion, but he did cause that I be rebellious, by use of means: Satan, Adam and sin. And this he did for his own purpose: The Gospel.
They also ignore that all such assertions depend on the determinative ability of mere chance, which notion, again, is logically self-contradictory. There is no accident.
