The second part of this work examines a number of applications of the theory. We present a new microscopic derivation of the intervalley deformation potentials within the tight binding representation and computes a number of conduction-band deformation potentials of bulk semiconductors. We have also studied the electronic states in heterostructures and have shown theoretically the possibility of having barrier localization of above-barrier states in a multivalley heterostructure using a multiband calculation. Another result is the proposal for a new "type-II" lasing mechanism in short-period GaAs/AlAs superlattices. As for our work on the optical properties, a new formalism, based on the generalized Feynman-Hellmann theorem, for computing interband optical matrix elements has been obtained and has been used to compute the linear and second-order nonlinear optical properties of a number of bulk semiconductors and semiconductor heterostructures. In agreement with the one-band elective mass calculations of other groups, our more elaborate calculations show that the intersubband oscillator strengths of quantum wells can be greatly enhanced over the bulk interband values.