Place fish in a glass pan and squeeze the juice from one lime over the fish. In a small bowl, whisk together garlic powder, cumin, cayenne and sea salt. Sprinkle over fish and gently rub the seasoning in. Allow the fish to marinate for 10 minutes or so.
Meanwhile, in a large bowl combine cabbage, onion, cilantro, juice from the lime, mustard, honey, salt and pepper. Toss to combine. Set aside.
Heat grill to medium-high and lightly oil grill-grate. Arrange tortillas in a stack and wrap with aluminum foil. Grill fish until cooked through, 3 to 4 minutes per side. Place tortillas on cooler part of grill (we used the top rack) until warm, 5 to 8 minutes, turning halfway.
For grilled avocado: Cut avocado in half and remove seed. Drizzle with fresh lime juice and brush lightly with olive oil. Gently place cut-side down and grill over hot coals for 2 to 3 minutes. Season with salt, to taste.
Break fish into large pieces. Taste slaw and season to your liking by adding more mustard, honey, salt and pepper if needed. Divide fish among tortillas and top with slaw, grilled avocado slices and your favorite salsa and hot sauce. Serve each taco with a lime wedge for squeezing over the taco before digging in. Enjoy!