Everything you've said assumes a basis for truth ascertained by investigation. Darwinistic presuppositions assume truth and falshood but is utterly impotent to account for its underlying basis - some absolute standard of truth. It must presuppose it as though it stood on its own. The Creationist OTOH presupposes God and is able to account for truth because he has a single, unified, rational starting point.
Neither evolution nor science holds to any absolute standard of truth. This is exactly what keeps science open to change. Since your premise is false, your conclusion that follows (il)logically from that is also false.