Bringing 12v Power to my Truck Bed

I've ordered a dual battery kit from @HeliMedic and am trying to figure out how I want to distribute power to the rear of the truck. I will be running an ARB Fridge back there as well as various accessories (power to the CVT tent/awning, USB outlets, portable water pump, lights, etc). Right now, this is the wiring diagram I have in mind. I'd like each cig socket (rated 15A) to be able to handle a full load. Since there will be 4 of these, plus some miniscule draw from the USB outlet/voltmeter, I figured I would use a 75A relay so I can control the whole thing from a master switch. The switch included in the panel doesn't appear to be weather-proof, so I will likely replace it with something better, which got me to thinking about placement. Ideally, this switch would be routed inside the cab, so no "outside forces" can tamper with it. This means I can put the relay in the engine bay somewhere, route the switch through a grommet I am already using the the compressor switch, and then just run cables to the rear fuse panel.



Questions:
Is this a good approach?
Also, from the wiring diagram, do you see any issues with the area in the dashed circle?
The switch will have a light, so I guess it needs a fuse as well?

Current Parts List:
10 Position Low-Profile Mini/APS Fuse Panel - $26.83
(I know there are better ones out there, but I chose this one since it shares the same fuse type as the truck.)

LiDiVi Dual USB Socket Charger 2.1A & 2.1A with LED Voltmeter + 12V Power Outlet+ ON-Off Toggle Switch, Four Functions Panel for Car Boat Marine RV Truck Camper Vehicle (Blue)

Dual USB Socket Charger (2.1A x2) with LED Voltmeter, 12V Power Outlet, Toggle Switch - $21.99
(Most USB outlets have one 1A, which seems useless, plus this one had a voltmeter, saving me one slot. Likely will replace the switch.)

3 Waterproof Car Cigarette Lighter Socket 12V Power Outlet with Three-hole Panel - $17.99
(This seems the most versatile - I can always get adapters)

Parts to Figure Out:
Reset-able Circuit Breaker
Relay(s)
Waterproof switch (if I leave it in the truck bed) or extra cig socket if I put the existing switch in the cab)

 

What about a cool "Battery Disconnect Isolator Master Switch" instead of a switch / relay combo?

Cllena Battery Isolator Disconnect Cut OFF Power Kill Switch for Marine Car Boat Rv ATV Vehicles

https://www.amazon.com/gp/product/B01IBOH5EA/

 

If you haven't purchased that fuse block, get one with a negative bus. It'll make for easier wiring.

$30 Blue Sea Systems 5025 ST Blade Fuse Block 6 Circuit with Ground and Cover

https://www.amazon.com/Blue-Sea-Sys...502208205&sr=1-2&keywords=blue+sea+fuse+block

 

Hmmm... This gives me food for thought. If I put a cut-off switch in the engine bay, no one can tamper with it. (I'm not concerned about people being malicious - It's more a concern of a kid who's done charging their gaming pad and flipping the switch off.) I'm wondering now if I need one at all? The circuit breaker can act as a switch, right?

I've had my eye on something like that, but I couldn't find one that uses APS (low-profile mini) fuses. I'm going to have to use a separate negative bus.