It looks like you are using a diode isolator. Are the battery charger
designed to be connected to an isolator? The problem is a diode isolator has a .2 - .7 volt drop across it. A regular alternator
with internal regulator
senses the voltage at the alternator on the output wire. If it's voltage setpoint is 14.1 volts, the battery would be charging
at 13.9 - 13.4 volts. It would take much longer to charge the battery.
A battery charger would go into float too soon.
If they have a voltage sensing wire that connects directly to the battery then there is no issue. Or some alternators had a second output post that accounted for the voltage drop.
Fuses that are at the device are intended to protect the device. You need fuses (or circuit breakers) as close to the battery as that size wire exists.
The fuse just off the house battery is theoretically sized to protect that big wire. When you get to the smaller wires it won't help.
The fuse at the device only works if the device shorts. If the smaller wire leading to it shorts, it can cause a fire without a fuse on that wire closest to the battery end.