I don't have any trouble finding giant corn locally. If you can't find them, hominy is a decent substitute. Start with dried or frozen. The canned product will be too soft.
Lima beans (fresh or dried) would be a great substitute for the fava beans. Just make sure to start with tender (not soft) cooked beans.
Rocoto peppers are hot! They are so flavorful, but proceed cautiously. Start by dicing one - or even half of one. You can add more if desired.
As I mentioned, we have taken this dish as a side dish to a party, but we have also enjoyed it as a main dish with the addition of grilled shrimp. Grilled chicken would be a great option as well.
Macronutrients (approximation from MyFitnessPal): 269 calories; 11 g protein; 15 g carbohydrates; 19 g fat.