The Force is not the fabric of reality itself. Otherwise that would make the Yuuzhan Vong are not apart of reality. As for the Flood, they are not constricted to the biological. The Logic Plague is a digitized version of the Flood infection that is transferred by the Flood's logic, and then by those infected by it. While true that the Death Star is very large and of great power, the Mantle's Approach is roughly 3 times bigger than it, and is noted as being one of the Forerunner's smaller ships. Then you have the Precursors, which are trans-sentient and whose creations are constructed out of Neural Physics, a fabric of existence that can only be destroyed or damaged by weapons that target neurological pathways. The only known weapon capable of such a feat being Halo.