I have never used a Dutchman, but your tanks could be plumbed in a few different configurations, mine has the kitchen sink, bathroom sink and shower plumbed together into the grey water tank, the toilet dumps directly into the black tank, Fresh is pretty self explanatory, that's your fresh (drinking) water, some have the bathroom sink plumbed into the black tank usually because of proximity to the black tank, some larger 5th wheels and class A's have 2 grey tanks,(I don't know how they're plumbed).
As far as your monitor, it tells you how much is in each tank, Empty? 1/3, 2/3, full, the battery tells you how much charge is left in the batteries, assuming they work, blank tank gages are notoriously incorrect.
The switch that says Pump is for the pump that pumps water from your fresh tank to your faucets.
As far as your tank dump valves, you've left me in the fog, as mine doesn't have "cables", they are a blade type valve with a straight rod that pulls to open the valve and pushes in to close, I have had to replace a handle as the originals are plastic, the replacement I got is metal.
