if I can play 'Mr Diagnosis' here for a minute, I would suggest that what you might have is a '12v shut off' switch that is not working properly, but that's just an educated guess.
all the items, with the exception of the water heater, work off of 12v from the HOUSE batteries. The reason that propane items are not working, is that they require the 12v 'spark' to start.
The other items that you mention that DO work, are probably powered from the CHASSIS batteries.
You may have TWO 12v shut off switches, one for the HOUSE batteries, and one for the CHASSIS batteries. You may have shut both off, and now only have the Chassis switch back on.
just my guess, though.
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