I still think you have to replace the wood and drywall when it gets soaked, the gypsum weakens. Did it soak through paneled walls into the drywall behind it? If so probably replace it all. The sun helps dry up wood but you don't have that option.
I'm not sure about a sealant but someone else may suggest something. An oil-based paint/enamel may be an option but I haven't tried it in this situation. If you can get the floor to dry, an oil/alkyd based primer may do the trick but then you have a painted floor. Go to a regular paint store to see what they say. There may be hope yet. I would try some things before replacement
I think you should contact the contractor who took the tank out. Between his warranty, his insurance, your insurance, you may get this worked out. File claims with all of them and keep us posted.