  The transport and optical properties of semiconducting transition metal
dichalcogenides around room temperature are dictated by electron-phonon
scattering mechanisms within a complex, spin-textured and multi-valley
electronic landscape. The relative positions of the valleys are critical, yet
they are sensitive to external parameters and very difficult to determine
directly. We propose a first-principle model as a function valley positions to
calculate carrier mobility and Kerr rotation angles. The model brings valuable
insights, as well as quantitative predictions of macroscopic properties for a
wide range of carrier density. The doping-dependant mobility displays a
characteristic peak, the height depending on the position of the valleys. The
Kerr rotation signal is enhanced when same spin-valleys are aligned, and
quenched when opposite spin-valleys are populated. We provide guidelines to
optimize these quantities with respect to experimental parameters, as well as
the theoretical support for \emph{in situ} characterization of the valley
positions.
