You are the one making grand claims so you should be the one supporting them. My position is that of the majority of professional Physics and Philosophy communities which is that the universe is deterministic and libertarian free will is a fantasy.
>I would also argue against determinism in some respects, but my thoughts about events being predetermined are a bit more complex
Well show some proof and claim your Nobel Prize.
> The argument isn't directly that knowledge requires free will, but rather that you can't, as a mere product of some chain of events, be a reliable source.
You are just saying this, it doesn't follow from any Philosophical argument that I can see Honestly I think your argument boils down to "The absence of free will makes me uncomfortable so therefore it can't be true," this isn't unique to you either most of the people on that side of the fence's arguments tend to come down to that.