Place caramels and hot water in top of double boiler. Heat and stir frequently until caramels are melted and sauce is smooth. Soften the gelatin in cold water and then dissolve in the hot caramel sauce. Add the salt and vanilla. Chill until slightly thickened. Whip chilled milk until fluffy. Fold in the caramel mixture and 1/2 cup of the chopped pecans. Pour into the baked pastry shell and sprinkle top with remaining nuts. Chill until firm.