Looks like you need to update your avatar...says "still looking"
I'd suggest contacting the manufacturer with your Vin number. They can likely send drawings showing where the frame members are supposed to be, etc... also plumbing diagrams and electrical.
The stuff I have form Thor isn't much more than schematic level, but still might prove useful.
I'd seriously doubt if the cabinetry is supporting the roof. I'm sure once you get digging in you'll be able to see better.... but I can imagine no way that this would make any sense
Depending on how far under it goes, perhaps you can get away with flush cutting the fridge bulkhead just at the floor and temporarily supporting so you can slide the old wood out and slide new wood in....saving from removing the fridge
Hope you found and solved the leak....
Good luck!
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