Lightly spray a 9-inch pie pan with cooking spray. Combine all crust ingredients in a mixing bowl until combined. Press the mixture firmly into the bottom and up the sides of the prepared pie pan and freeze crust for 30 minutes.

Combine the cream cheese and sweetened condensed milk in a large mixing bowl and beat with an electric mixer until smooth. Add the remaining filling ingredients and beat to combine. Pour filling into the frozen crust, then cover loosely with plastic wrap and refrigerate for 2 hours.

Combine the rhubarb and 1/2 cup of the water in a medium saucepan set over medium heat. Bring to a boil, stirring occasionally, then reduce heat to low and simmer until rhubarb is tender, about 10 minutes. Remove from the heat, drain the rhubarb, then return it to the pan.

Place the remaining 2 tablespoons water in a small bowl and sprinkle the gelatin over the top. Let stand 1 minute to soften. Stir the gelatin-water mixture and the 1/2 cup granulated sugar into the rhubarb and set the pan over medium heat. Bring to a boil, stirring often. Remove from the heat and stir in the lemon juice. Pour the rhubarb mixture into a bowl and refrigerate until thickened.

Stir the sliced berries into the thickened rhubarb and spoon over the cheesecake. Top with additional sliced strawberries if desired. Cover loosely and refrigerate for 2 hours (or overnight), until topping is set. Serve.