  We study the linear, second-order nonlinear (NL) current and voltage
responses of a two-dimensional gapped semi-Dirac system with merging Dirac
nodes along the $x$ direction under the influence of a weak magnetic field
($B$), using the semiclassical Boltzmann formalism. We investigate the effect
of band geometric quantities like Berry curvature and orbital magnetic moment
in the responses up to linear order in $B$. We derive exact analytical
expressions of the linear magnetoconductivities, second-harmonic NL anomalous
Hall (NAH), and anomalous velocity and Lorentz force induced (NAL)
conductivities, unveiling their dependence on Fermi energy and a gap parameter
$\delta_0$. For $\delta_0 > 0$, the Fermi surface topology changes at a
particular Fermi energy, which is reflected in the nature of conductivities
through a kink. The ratio of NAL and NAH conductivities is found to be
independent of $\delta_0$ and inversely related to Fermi energy. The NL dc
current exhibits distinct orientations depending on the Fermi energy, magnetic
field, polarization of the electromagnetic wave. In the presence of magnetic
field, the NL dc current vector can be rotated through large angles on
variation of Fermi energy. For high Fermi energies, the NL dc current is
directed nearly along the $y$-axis for $x$-polarized and low-frequency
circularly polarized light, whereas it aligns close to $x$-axis for
high-frequency circularly polarized light. These orientations of the NL dc
current are predominantly governed by the mirror symmetry of the system along
the $x$ direction. Additionally, we also study the NL voltage responses of the
system by applying current along the $x$ and $y$ directions. The system
exhibits asymmetry in the $B$-dependencies of the NL resistivities, which may
serve as an experimentally relevant signature for band geometric quantities and
merging Dirac nodes in such systems.
