For the caramel: In a heavy-bottomed 4-quart saucepan, bring 1/3 cup plus 1 1/2 tablespoons water, the sugar and corn syrup to a boil, wiping the sides of pan with a wet pastry brush occasionally until the mixture turns a dark amber color. Carefully and slowly add the heavy cream, stirring with a whisk, then add the butter, vanilla and salt. Bring back to a boil and cook for another 2 to 3 minutes. Cool the caramel for 10 minutes, then add the orange oil and food coloring. Cool completely before using.
For the gummy tails: In a small liquid measuring cup, bloom the gelatin in 1/2 cup cold water for 5 minutes. Warm the mixture in a microwave on high until the mixture is liquid and smooth, 15 seconds. Add the orange oil, mixing it in well.
For the shells: Temper the chocolate. Fill the mouse molds with the chocolate and knock them carefully on a hard surface to release any air bubbles. Pour out the excess chocolate back into the bowl of tempered chocolate.
Scrape the flat portion of the mold to clean off the excess chocolate. Cool the mouse shells to harden completely.
Place the cold caramel in a piping bag, with a small hole cut in the end. Pack the pumpkin seeds into the body cavities of the chocolate shells, then pipe in the caramel until the filling is 1/16-inch below the top. Pour more tempered chocolate over the filling, and scrape the excess again, then let cool and set up completely. Carefully dig out any chocolate that may have gotten into the tail portion of each mouse mold. Clean them with cheese cloth until shiny. Pour the liquid gelatin mixture into the tail portion of each mouse mold. Let cool and set up completely. Release the mice from their molds by gently tapping the mold, right-side up, until they all come out. If any of the gelatin tails do not adhere to their chocolate bodies, use a small amount of tempered chocolate to glue them back on.