Mix expands somewhat on freezing (depending on how much air your ice cream maker churns in), so you may have to freeze in multiple batches or halve the recipe. Make sure you have enough containers to store the finished product.
Reduced-fat peanut butter is fine also. If using natural peanut butter, adjust sugar and salt accordingly.
This recipe can be made dairy free. Swap out all the dairy with plain soymilk (3 cups--I use the shelf-stable store-brand variety and think it's great). Before heating, stir in a heaping teaspoon of cornstarch, making sure there are no lumps. Bring to the boil briefly so cornstarch can thicken the soymilk to the consistency of cream (nice cheat!). Turn off heat and stir for a few minutes to cool the soymilk mixture before turning the heat back on medium-low and proceeding with the recipe. This step is necessary because adding the tempered eggs to boiling liquid will break the custard.