There is only one choice...
To run the Fridge w/o generator, He will need an inverter, Likely 1,000 watt or more, and LOTS of batteries, I'd say 3 pair of GC-2 at the very minmum, likely more.
To run the PAP machine,,, He needs to make sure it can run on battery power and install the needed connectors near the bed.
or, Same inverter
But why dual convert (12 volt to 120 volt to 12 volt) if you don't have to.
He will also need to test the system to insure the batteries will last the night cause folks who use a PAP. if it looses power, can easily wake up dead. and that is not a good thing.
(I got,, Well lucky is not necessarly the word, but I was examined by both a cardiologist, who worked long and hard to keep me alive (clearly successfully) and a pulmanologist if I've spelled it right (lung and resperation) who did nothing for me but schedule a sleep study he felt I did not need.
The cardiologist and my Primary care, both based on the heart problems were sure I had severe Apena.
The sleep study results: NO APENA... None, Zip, Nada, Don't have it.
I told the sleep doc that I felt that if I were to make a bet, I'd bet on the Lung& Resperationb doctor. After all, it's his specality.
He said he'd have bet with the other two.
But no matter.. I WON.