  We investigate reheating in the string-theory-motivated K\"ahler Moduli
Inflation I (KMII) potential, coupled to a light scalar field $\chi$ and
produce constraints and forecasts based on Cosmic Microwave Background (CMB)
and gravitational wave observables. We implement a Markov Chain Monte Carlo
(MCMC) sampling method to compute the adopted model's parameter ranges allowed
by the current CMB observations. Floquet analysis and numerical lattice
simulations are performed to analyze the nonlinear effects of the model's
(p)reheating phase. We derive bounds on the $\Lambda$CDM parameters $A_s$,
$n_s$, $n_{\mathrm{run}}$, and $r$ based on \textit{Planck} results, finding
that correlations between model parameters severely constrain the range of
these parameters allowed within this model. While the KMII potential's
non-vanishing minimum may provide a possible source for the observed dark
energy density $\rho_{\mathrm{DE}}$ this cannot be tested with current
observations. We estimate the $95\%$ CI bounds on the inflaton mass $m_{\phi}$
and reheating temperature $T_{\mathrm{reh}}$ to be $2.1 \times 10^{13} \,
\mathrm{GeV} \lesssim m_{\phi} \lesssim 3.2 \times 10^{13} \, \mathrm{GeV}$ and
$T_{\mathrm{reh}} \gtrsim 1.8 \times 10^{3} \, \mathrm{GeV}$, respectively. We
observe {both} self-resonance and parametric resonance instability band
structures in our Floquet analysis results. Finally, we do not observe any
formation of oscillon configurations in our lattice simulations; however, our
results predict a stochastic gravitational wave background generated during
preheating that would be observable today in the $10^{9}$ - $10^{11} \,
\mathrm{Hz}$ frequency range.
