  The recent observations of a stable molecular condensate emerging from a
condensate of bosonic atoms and related "super-chemical" dynamics have raised
an intriguing set of questions. Here we provide a microscopic understanding of
this unexpected stability and dynamics in atom-molecule superfluids; we show
one essential element behind these phenomena is an extremely narrow Feshbach
resonance in $^{133}$Cs at 19.849G. Comparing theory and experiment we
demonstrate how this narrow resonance enables the dynamical creation of a large
closed-channel molecular fraction superfluid, appearing in the vicinity of
unitarity. Theoretically the observed superchemistry (\textit{i.e.}, Bose
enhanced reactions of atoms and molecules), is found to be assisted by the
formation of Cooper-like pairs of bosonic atoms that have opposite momenta.
Importantly, this narrow resonance opens the possibility to explore the quantum
critical point of a molecular Bose superfluid and related phenomena which would
not be possible near a more typically broad Feshbach resonance.
