For crust: Preheat oven to 350°F.
Coat 9" glass pie dish with cooking oil spray.
Using pulse, finely chop 1 cup pecans in food processor; transfer to medium bowl. Mix in graham cracker crumbs and sugar. Add melted butter; blend until evenly moistened. Press mixture firmly into bottom and up sides of prepared pie dish.
Bake crust until golden brown, about 12 minutes. Cool completely. Freeze at least 1 hour.
*Sauce and filling* Bring 3/4 cup brown sugar, 3/4 cup heavy cream and 3 Tablespoons dark corn syrup to boil in heavy medium saucepan, whisking until sugar dissolves. Boil caramel 5 minutes, whisking occasionally. Turn off heat; whisk in butter, vanilla, and salt. Cool completely.
Slightly soften vanilla ice cream in microwave on low in 10-second intervals. Spread ice cream evenly in frozen pie crust. Return to freezer. Freeze completely.
Spread all but 1/4 cup caramel over ice cream. Freeze pie until ice cream and caramel are firm, at least 1 hour or overnight. Cover and save the remaining 1/4 cup caramel for garnish later on.
*Ganache topping* Combine chocolate, cream, and corn syrup in medium metal bowl. Place over saucepan of simmering water and whisk until melted and smooth. Remove from heat. Whisk in vanilla and salt. Cool ganache at room temperature until thick but still pourable, about 30 minutes.
Pour ganache evenly over frozen pie. Decorate with pecan halves. Freeze until ganache is firm, at least 45 minutes. Drizzle decoratively with 1/4 cup reserved caramel.
Let pie stand 10 minutes at room temperature before serving.