RE: Battery Draining
IIRC before you replaced the starting battery you put a meter on it and
found about a 1 amp or better drain/current flow with everything turned
off.  If that was not chased down and corrected your new battery is going to
go dead.

The aux battery, when properly wired in, provides voltage for the
refrigerator but only for about 2 to three hours max.  If additional wiring
changes are made then all interior lights, the radio, and the cigarette
lighter are also moved to the aux battery.  Many people add additional 12v
outlets, like the cigarette lighter, and wired directly (with fuse) to the
aux battery to use for computers, TV sets etc.  That way there is no danger
of running down the starting battery.

If your aux battery is in fact a deep cycle and is to tall for the battery
compartment it may well be an Optima.  Is the top of the battery yellow or
blue plastic rather than black?