  We use Kohn-Sham spin-density-functional theory to study the statistics of
ground-state spin and the spacing between conductance peaks in the Coulomb
blockade regime for both 2D isolated and realistic quantum dots. We make a
systematic investigation of the effects of electron-electron interaction
strength and electron number on both the peak spacing and spin distributions. A
direct comparison between the distributions from isolated and realistic dots
shows that, despite the difference in the boundary conditions and confining
potential, the statistical properties are qualitatively the same. Strong
even/odd pairing in the peak spacing distribution is observed only in the weak
e-e interaction regime and vanishes for moderate interactions. The probability
of high spin ground states increases for stronger e-e interaction and seems to
saturate around $r_s \sim 4$. The saturated value is larger than previous
theoretical predictions. Both spin and conductance peak spacing distributions
show substantial variation as the electron number increases, not saturating
until $N \sim 150$. To interpret our numerical results, we analyze the spin
distribution in the even $N$ case using a simple two-level model.
