Line an 8×8-inch pan with parchment paper and set aside.
In a medium saucepan over low–medium heat, combine the 2 cups milk chocolate wafers, 1/2 cup peanut butter, and 1 1/2 tablespoons of the evaporated milk; stir constantly with a rubber spatula until the mixture is thick and fluffy and fully combined.
Reduce the heat to low, fold in the 7 ounces marshmallow fluff, and stir until completely combined and smooth.
Pour this chocolate-peanut butter-marshmallow layer into the prepared pan and smooth; it will self-level.
Evenly sprinkle 1 cup lightly salted roasted peanuts over the chocolate layer and set the pan aside.
In a microwave-safe bowl, combine the soft caramels (about half of a 10.8 oz bag) with the remaining 1 1/2 tablespoons evaporated milk.
Microwave the caramels at 50% power for 1 minute, stir (it will be thick), then continue heating in 30-second bursts at 50% power, stirring between bursts, until the caramel is smooth and pourable.
Pour the warm caramel evenly over the peanuts, spreading gently so it covers the nuts without disturbing the layer below.
Refrigerate the pan until firm, about 4 hours or overnight.
Lift the chilled slab from the pan using the parchment paper and place on a cutting surface; cut into 12 bars (make one lengthwise cut, then five crosswise cuts for 12 pieces) using a sharp knife.
Place the cut bars on a parchment-lined baking sheet and return the sheet to the refrigerator to keep the bars chilled while you melt the dark chocolate.
In a medium microwave-safe bowl, heat 1 1/2 cups dark chocolate wafers at 50% power for 1 minute, add 2 tablespoons vegetable oil, stir, then continue heating in 30-second bursts at 50% power, stirring until the chocolate is silky smooth.
Using two forks or dipping tools, dip each chilled bar into the melted dark chocolate to coat completely, shake off excess, and return to the parchment-lined sheet.
Refrigerate the coated bars until the chocolate is fully hardened, about 30 minutes, then serve.