We extend previous work on N=2 Chern-Simons theories coupled to a single
adjoint chiral superfield using localization techniques and the F-maximization
principle. We provide tests of a series of proposed 3D Seiberg dualities and a
new class of tests of the conjectured F-theorem. In addition, a proposal is
made for a modification of the F-maximization principle that takes into account
the effects of decoupling fields. Finally, we formulate and provide evidence
for a new general non-perturbative constraint on spontaneous supersymmetry
breaking in three dimensions based on Q-deformed S^3 partition functions. An
explicit illustration based on the known analytic solution of the Chern-Simons
matrix model is presented.Comment: 42 pages, 12 figures; v2 mostly cosmetic changes, references added;
v3 minor changes to match the published version in NP