The shunt is part of the battery wiring and needs to be connected to the neg post with at least #4 wire since it carries the total amps of everything on the outboard end of the shunt. I use a store-bought short piece of "starter cable" that has the two ring terminal lugs already on it for that connection.
In the OP you seem to be mixing up your units AH, volts? Hard to tell what the situation is. I suspect the equipment you have would work, but there is some kind of operator error somewhere. Can you ask another RVer at a campground who seems to have a good set-up to look at yours?
