“And if the Immaculate Conception was not a true, historical fact, then I’m not sure you can even say with any definitive authority that Jesus Christ was Divine.”
Why? There is no scriptural basis for the Immaculate Conception (”In the Constitution Ineffabilis Deus of 8 December, 1854, Pius IX pronounced and defined that the Blessed Virgin Mary “in the first instance of her conception, by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved exempt from all stain of original sin”).
Anything short of perfection in His human nature — including His mother and His conception — would be incompatible with the notion that Jesus Christ was Divine.