We report new observations toward the hyper-luminous dusty starbursting major
merger ADFS-27 (z=5.655), using ATCA and ALMA. We detect CO 2-1, 8-7, 9-8, 10-9
and H2O(321-221) emission, and a P-Cygni-shaped OH+(11-01) absorption/emission
feature. We also tentatively detect H2O(321-312) and OH+(12-01) emission and
CH+(1-0) absorption. We find a total cold molecular mass of M_gas = (2.1+/-0.2)
x 10^11 (alpha_CO/1.0) Msun. We also find that the excitation of the
star-forming gas is overall moderate for a z>5 dusty starburst, which is
consistent with its moderate dust temperature. A high density, high kinetic
temperature gas component embedded in the gas reservoir is required to fully
explain the CO line ladder. This component is likely associated with the
"maximum starburst" nuclei in the two merging galaxies, which are separated by
only (140+/-13) km/s along the line of sight and 9.0 kpc in projection. The
kinematic structure of both components is consistent with galaxy disks, but
this interpretation remains limited by the spatial resolution of the current
data. The OH+ features are only detected towards the northern component, which
is also the one that is more enshrouded in dust and thus remains undetected up
to 1.6 um even in our sensitive new HST/WFC3 imaging. The absorption component
of the OH+ line is blueshifted and peaks near the CO and continuum emission
peak while the emission is redshifted and peaks offset by 1.7 kpc from the CO
and continuum emission peak, suggesting that the gas is associated with a
massive molecular outflow from the intensely star-forming nucleus that supplies
125 Msun/yr of enriched gas to its halo.