[cksquare]

"Unicorns exist" and "unicorns don't exist" are not factual statements, they are premises. Establishing the truth or falsehood of either has nothing to do with my opinion of the existence of unicorns--unicorns would not exist in spite of my fervent desire for them to be real, or if I just happened to think they were really cool.

Assuming that you believe in the miracles of the old and new testaments, how would such things be proven false? For them to be positive evidence for the existence of God, we should at least be able to imagine how we'd go about refuting them.