This is what I did for a repair on my similar past thor 17 yrs ago, My Floor construction was very thin sheet metal,lauan,styrofoam, lauan then topped with linoleum all glued.
I ended up dremming out patches of the sheet metal, replaced with bug screen. This allowed the wood to dry out underneath and on the top side I cut out the linoleum, allowed the wood to dry out and topped with new plywood, (I went wall to wall with the new plywood, I did not go under the walls) then secured to old floor and topped with those stick on linoleum tiles. This was not a cure all but certainly a heck of a good remission repair. I ended up getting 11 years out of a poorly constructed trailer.
I did catch my leak relatively early, your situation is proberly different, so use the info with a grain of salt
good luck
Mike
