Theism (whether Christian, Jewish or Muslim) holds that God by wisdom created the world. The origin of the world and its subsequent ordering thus result from the designing activity of an intelligent agent - God. Naturalism, on the other hand, allows no place for intelligent agency except at the end of a blind, purposeless material process. Within naturalism, any intelligence is an evolved intelligence. Moreover, the evolutionary process by which any such intelligence developed is itself blind and purposeless. As a consequence, naturalism makes intelligence not a basic creative force within nature but an evolutionary byproduct.
Aside from your objections, I think Dembski really is presenting a false dilemma here. In theistic evolution, the idea of underlying purpose is there, albeit perhaps materially inscrutable.
To deny that nature is stochastic is to ignore voluminous evidence. But stochastic does not imply purposeless. That's a metaphysical assumption.
Dembski's writings seem to have a consistent theme of trying to shoehorn science into a fairly rigid theology. He seems utterly uncomfortable with mystery, ironically resembling the strong atheists in that regard.
™ Version 4.2
