Cannot locate breakers and fuses

Follow the shore power cord. It will terminate at the breaker panel. The converter is probably near that.

You may have a short but all MHs have parasitic loads on the battery. Think CO and propane detectors. If you can't plug the MH in every few days you should probably disconnect the negative lead of the battery. The reason you should disconnect the negative lead is that there is a very real risk of causing a short circuit when using a metal wrench on the positive terminal.

You probably have a single stage converter. That will take a long time to recharge the battery, think days. If you can only plug it in for a few hours the battery is not getting charged and thus will be discharged in a short time.

First question. The Ford fuse panel, for chassis only, has nothing to do with the house part, is located inside the drivers compartment, under the dash on the fire wall, same as most cars. On our 06, there is also a breaker and distribution panel under the hood near the drivers side fender.

The MH part of the RV is usually one combined unit, 120v inlet, convert 120 to 12v for house and charging the house battery. This is usually a steel faced panel with flip open door. It will have circuit breakers for the 120v system (and main input breaker). The second part of the unit will have automotive style fuses for the 12v part of the MH.
This could be located anywhere in the MH, but usually near the coach/house batteries. Our c-class also has a secondary panel for the house, which is located at the back of an outside storage compartment, behind another metal door.

Two chassis batteries, quite possible if your c-class has the diesel engine. Our old Ford E-series based ambulance had 3 chassis batteries, two as you said plus a third under the left battery, accessed only by taking of the grill and headlight, the mechanics really loved checking that one.

Beverley and Ken

There may be no "short". Battery loses charge because there are devices that remain connected when everything is off, be it a truck or house battery. Good news is that they - usually - don't need to be connected when left in storage for several days. Take the cables off the battery, or at least, the +Pos cable.

Two batteries are probably your House batteries, the other is the truck battery.

Two batteries are probably your House batteries, the other is the truck battery.

One of those batteries is your HOUSE battery.