Hey Grant! There should be a battery isolator between the house and engine batteries that allows the alternator to charge the house batts, but doesn’t allow the house to draw down the engine battery. The Clark models also had a disconnect switch to disconnect the engine battery when not in use (don’t know if this is true for Kents like yours).
I suspect the interior plugs should already work when powered by the generator. If you want them to be run off the house battery bank, you’ll need to add an inverter into the system.