Power Inverter Setup

My 2012 Cascadia came with a warning to only use a low voltage disconnect inverter. Do you know if this implies that the inverter needs to be wired into one of the LVD circuit set up in the truck, or can it be wired directly to the batteries as long as the inverter has a LV shutoff? Also I want to put in circuit breaker(s). I was thinking 120amp but am not sure. Also the inverter has 2 sets of cables, should I add a breaker/fuse to each positive line? Also the directions are for a single battery and say to hook both reds to the positive post and both blacks to the neg post. As I have 6 batteries should I attach to different batteries for each set of wires? The biggest appliance I plan on using is an 1100watt micro and maybe a 1200watt coffee pot.
Thanks