For Lemon Curd: Whisk eggs and egg yolks in medium bowl. Melt butter in medium metal bowl set over large saucepan of simmering water. Whisk in sugar, lemon juice, lemon peel, and salt; gradually whisk in egg mixture. Whisk until thick and thermometer inserted into curd registers 178-180 degrees F, about 8 minutes. Transfer to small bowl. Press plastic wrap on top of curd; chill 4 hours. (this can be made 2 days ahead. Keep chilled.).
For Crust: Preheat oven to 400 degrees F. Mix pecans, sugar and butter in medium bowl until moistened. Press pecan mixture onto the bottom and up sides of a 9-inch diameter glass pie dish (mixture will be crumbly). Bake until crust is lightly toasted, about 12 minutes (crust will slip down sides of dish). Use back of spoon to press crust back into place. Cool crust on rack. Freeze crust 30 minutes.
To put it all together: Put ice cream over frozen crust; spread into even layer, spread lemon curd over ice cream; freeze about 2 hours, until firm. Or for a prettier pie, put 1 1/2 cups ice creams then 1/2 the lemon curd, then rest of ice cream and top with remainder of lemon curd.
When ready to serve, spread whipped topping over lemon curd.