This study proposes a unified physical framework integrating conservation-based spatial foundations with discrete spatial quantum mechanics. By leveraging spatial quantum's localized splitting, adjacent capture, and density gradient effects, we develop a coherent explanation for the microscopic origins of gravity, cosmic expansion, dark matter, dark energy, and vacuum energy divergence. The theoretical mechanism posits that the total spatial volume remains strictly conserved, with space composed of indivisible fundamental units called spatial quantum. To maintain energy, momentum, and angular momentum conservation, bound matter continuously undergoes virtual particle processes—quantum information exchanges that require spatial quantum as the minimal physical degree of freedom, leading to their gradual increase over time. Gravity emerges as a geometric dynamics effect driven by spatial quantum density gradients, while cosmic expansion manifests as the continuous fragmentation of this conservation-based foundation into quantum units, observable through the light-cone causality structure. This model serves as a microscopic extension and refinement of general relativity, effectively addressing black hole singularities and Big Bang singularities. Without introducing dark matter particles, dark energy scalar fields, or additional gravitational corrections, it provides a self-consistent explanation for observed phenomena including galactic rotation curves, gravitational lensing, bullet clusters, and super-diffuse galaxies, while mitigating vacuum energy density divergence-induced "vacuum catastrophe" issues. The theory satisfies Lorentz covariance and local causality, featuring a relatively closed underlying structure with minimal assumptions, offering a potential pathway toward constructing a complete, singularity-free unified description of gravity and cosmology.