  We present a Monte Carlo based analysis of the combined world data on
polarized lepton-nucleon deep-inelastic scattering at small Bjorken $x$ within
the polarized quark dipole formalism. We show for the first time that
double-spin asymmetries at $x<0.1$ can be successfully described using only
small-$x$ evolution derived from first-principles QCD, allowing predictions to
be made for the $g_1$ structure function at much smaller $x$. Anticipating
future data from the Electron-Ion Collider, we assess the impact of
electromagnetic and parity-violating polarization asymmetries on $g_1$ and
demonstrate an extraction of the individual flavor helicity PDFs at small $x$.
