The recent long-term shutdown of Japanese nuclear reactors has resulted in a significantly reduced reactor (nu) over bar (e) flux at KamLAND. This running condition provides a unique opportunity to confirm and constrain backgrounds for the reactor (nu) over bar (e) oscillation analysis. The data set also has improved sensitivity for other (nu) over bar (e) signals, in particular (nu) over bar (e)'s produced in beta-decays from U-238 and Th-232 within the Earth's interior, whose energy spectrum overlaps with that of reactor (nu) over bar (e)'s. Including constraints on theta(13) from accelerator and short-baseline reactor neutrino experiments, a combined three-flavor analysis of solar and KamLAND data gives fit values for the oscillation parameters of tan (2)theta(12) = 0.436(-0.025)(+0.029), Delta m(21)(2) = 7.53(-0.18)(+0.18) x 10(-5) eV(2), and sin (2)theta(13) = 0.023(-0.002)(+0.002). Assuming a chondritic Th/U mass ratio, we obtain 116(-27)(+28) (nu) over bar (e) events from U-238 and Th-232, corresponding to a geo (nu) over bar (e) flux of 3.4(-0.8)(+0.8) x 10(6) cm(-2) s(-1) at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo (nu) over bar (e) rate.