I think these are great questions - not in the 'who cares' or 'too complex' basket at all......
My take on them is that you're pointing to an epistemological problem which arises out of the claim that Buddha's have omniscience: having sufficient knowledge of all causes and effects necessarily implies something about the nature of all causes and effects.
But I think it is far better to approach the topic of causes and effects from the metaphysical point of view, rather than the epistemological: far more is written from that perspective, it is therefore more deeply and systematically cached out. The epistemic capacities of Buddha's, is in comparison, rather more speculative. I suppose I am tempted to ask: what is the epistemic basis for that
Buddhism clearly does not assert a deterministic view of causality: I would go as far as to say that the entire soteriological logic of all Buddhisms, rests on the basic premise that agents (karmic 'doers') always have the capacity to cultivate different cetana's
(intentions) and undertake different karma's
(actions). Liberation is only possible on that basis - it rests on the assumption that agents who are subject to karma have enough agency to do something about that subjection.
So, I think that that view of karma/causality is far more central to most Buddhism's than the epistemological claim that Buddha's are endowed with omniscience.
If a Buddha knows what choices I'm going to make before I make them, then I don't have agency to make choices; they are not choices in any meaningful sense. If I lack the agency to make choices, I also lack the agency to move in the direction of liberation. That line of thought takes us down a dodgy path that many (especially medieval) theists went down.
You're happy to accept a logic contradiction ~ I would suggest maybe a deeper investigation into what it is meant by Buddha's having omniscience. Something I'm not particularly well equipped to pursue....