I was shown how to remove a stuck forend from a sxs by a gunsmith/stockmaker friend. He took a tapered piece of hardwood, in this case about 12" long, 1/2" high at the blunt end, tapering to nothing, 1/4" wide, pushed the thin end under the forend tip and tapped the wedge with a rubber mallet and the forend popped off easily and no metal was scratched. Try that.
Mike