I would take this step at a time. I would also avoid using words such as "ridiculous" as AF may well be correct and you have no idea what ATC issues there may have been.
As OP was delayed by more than 4 hours at his final ticketed destination, e.g. YUL, EC 261/2004 compensation of EUR 600 is due unless the delay was the result of extraordinary circumstances. I would restate the claim in those terms. If denied again, you may ask AF to voluntarily produce the records demonstrating the ATC delay to you in lieu of a claim which you could make in either Greece or France. The burden would be on AF to prove the existence of the delay, not on you to disprove it. But, to be frank, it is not going to take much for AF to lay this out, so do not go spending those funds.
Whatever the reason for the delay, AF did have a duty of care to you for the hotel and intervening meals. I take it that AF either provided vouchers or has or is willing to reimburse for those.