To fix the gap between wing and fuse how about this-
I want to add white epoxy to the wing to fill the space against the fuse. I would put plastic wrap over the fuse where the wing seats then roughen the wing where it goes against the fuse and apply white epoxy to the wing and push it against the fuse where I put plastic wrap on it. After it set I would trim the epoxy and cover with white Ultrakote.
I think it would work, but would it be ok strength wise?