Rinse the halibut steaks under cold running water. Place in a shallow glass or ceramic baking dish large enough to hold the fish in a single layer. (Alternatively, you can marinate the halibut in a sturdy resealable plastic bag.)
Make the marinade: In a mixing bowl, combine the orange juice, pineapple juice, rum, Traeger Jerk Rub, and the brown sugar. Slowly whisk in the vegetable oil.
Pour the mixture evenly over the fish, turning the fish to coat both sides. Cover and refrigerate for 2 hours (no longer or the acids in the marinade will begin to "cook" the fish).
Make the Pico de Gallo: In a mixing bowl, combine the tomato, onion, jalapeno, garlic, cilantro, and lime juice; stir Add salt, about 1/2 teaspoon to start. Taste, then add more salt, lime juice, or jalapeno if desired.
Start the Traeger on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to High (400 or 450F) and preheat, lid closed, for 10 to 15 minutes. Generously oil the grill grate with vegetable oil so the fish doesn't stick.
Remove the fish steaks from the marinade and lightly pat dry with paper towels. (If you love spicy flavors, dust the steaks on both sides with more Traeger Jerk Rub.)
Arrange the steaks on an angle on the grill grate. Grill for 6 to 8 minutes. Turn the fish with a thin-bladed spatula and continue to cook until the fish flakes easily when pressed with a fork, about 6 minutes more.
Transfer to a platter or plates and serve with the Pico de Gallo.