As you describe it, it sounds like the cabin is on a post or crawl space foundation? Insulate the kitchen floor again, preferably with styrofoam, and then ensure that rats and mice can't gnaw on it, preferably with mouse mesh.
The walls seem to be straightforward to tackle. Remove old paneling, install a vapor barrier, frame up, load more insulation, install new paneling.
Clear out the attic, install a vapor barrier everywhere, fill the attic with insulation until it overflows.
Now, many people from Byggahus will likely come with various objections to what I've written, since it's an eternal debate about whether to have a vapor barrier, vapor brake, which materials to use, etc., etc. The brutal truth is that no one really knows yet today what is optimal, but I believe what I've written above comes closest, based on the knowledge we have today.