First place I'd look is inside the compartment where the water heater itself is located. It is easily accessible from the outside. Once you are looking at the water heater, have someone turn the water on briefly while you are observing. I have seen a picture of one that was split wide open from freezing .... the water heater is quite thin (aluminum IIRC) and won't withstand the hoop stress created by freezing water as it expands.
Beyond that, there is access to the area of the water heater bypass valve by removing the inside panel under the refrigerator and just above the electrical panel there on the passenger side (it is about 4" X 24".) It is crowded in there though, with heater hoses to and from the engine but that is where the the water heater bypass valve is located for winterizing.
The low point drains for mine are under the bathroom sink (remove the plywood panel to access) but it sounds like your leak is more likely on the starboard side.
Good luck with the detective work. Let us know how it all gets resolved, pls.
Ed Sievers, Denver, CO
07 WGO 31ft Class C "Outlook"; Toad: '16 Soul with 6-spd DIY
"Be the person you needed when you were younger"