Build a medium-hot fire in a charcoal grill, or heat a gas grill to high.
Place shrimp and lobster in a large bowl. Drizzle with 2 tbsp oil and season with salt.
Mix onion and 2 tbsp lime juice in a small bowl.
Grill shrimp until just opaque in center, about 2-3 minutes per side. Transfer to a large plate.
Grill lobster tails, flesh side down, until slightly charred, 1-2 minutes. Turn flesh side up and grill until just opaque in center, about 5 minutes longer. Add to plate with shrimp and let rest for 5-10 minutes.
Remove lobster meat from shells and cut into 1 inch pieces.
Drain red onion and place in a large bowl. Add 3 tbsp lime juice, 2 tbsp oil, jicama, greens, tomatillos and cilantro. Season with salt and more lime juice.
Add seafood and toss to coat. Drizzle with chile oil and garnish with cilantro.