I'm familiar with Plantinga's argument that theism is properly basic. That fideism has nothing to do with justifying Christianity by appealing to the resurrection as evidence. If theism is properly basic, there's no rational justification of the belief that God exists (contrary to Plantinga's ad hoc notion of "rational justification" that's independent of evidence). Indeed, I've argued on existentialist grounds that theism isn't supposed to be rational. In that case we should evaluate religions on ethical and aesthetic grounds.

I haven't read that book by Plantinga on the conflict between science and religion. But I see from the description on Amazon that "Plantinga argues that we might think about arguments in science and religion in a new way--as different forms of discourse that try to persuade people to look at questions from a perspective such that they can see that something is true. In this way, there is a deep and massive consonance between theism and the scientific enterprise."

That looks like a postmodern turn. Science as a "persuasive discourse"? That's a muddying of the waters to put science and religion on equal footing. By that logic, science and pseudoscience aren't in conflict since both are discourses that aim to convince you that something is true. It just glosses over the cultural, practical, and other conflicts between these things.

I don't know where you're getting your data from, but the question of changing demographics is another red herring, having to do with how the pollster's questions are phrased, and with who's having the most babies. If religious people reproduce more than secularists, and indoctrinate their children, does that increase the odds that theism is true? If not, who cares about it? Why bring it up here?