Remove the ice cream from the freezer and let it soften slightly. Mix in the pecans, peanut butter cups and peanut butter candy bars. Pour the ice cream mixture into the crust. Cover with foil and freeze until very hard, about 1-2 hours.
For the sauce: Mix the brown sugar, half and half, butter and salt in a saucepan over medium heat. Cook, while whisking, until thicker, 5-7 minutes. Add vanilla and cook another minute to thicken. Pour the sauce into a jar and refrigerate until cold. The sauce will thicken as it gets colder.
Spoon the caramel sauce over slices of pie and sprinkle with pecans.