Thank you all for all of your responses! Really looking forward to trying this out. I apologize for being so clueless but they didn't teach electricity to women in the '50s here. I did learn to cook, clean and sew hems and the cooking came in handy later on.
Here are some responses to the questions you asked, Marko. Really appreciate all your help.
Under the hood, I have two batteries that say EVGC 220A AM 6v 220 AH. I guess these are the coach batteries. The engine battery is under the drivers' seat with the inverter, right?
The refrigerator is a Norcold DEO788B. It's label reads:
Rating AC 120 V, 0.8 A, 60Hz
Courant Nominal DC12/24V 3.0/1.5 A
So I guess it is a Dual Voltage Refrigerator but prefers to run on an AC source when available.
My roadtrek also has 750 watt inverter and a 2500 watt propane generator but I have no idea when I should have them on.
There is a 12V outlet in the ceiling above the bed that I thought I would use for my CPAP machine.
Marko, is the converter that you sent the link to the same as this one? CPAP.com - DC Converter 24V 90W For AirSense™ 10 and AirCurve™ 10 Machines
I'm just looking for the simplest resolution and not interested in carrying a battery booster pack if I can help it.