Using the back of a chef's knife, lightly smash lemongrass, then thinly slice. Combine lemongrass, chile, garlic, orange juice, fish sauce, brown sugar, and 4 tablespoons vinegar in a small bowl. Pour half of marinade into a large resealable plastic bag; reserve remaining marinade.
Prick pork chops all over with a fork and add to bag; seal and turn to coat. Let marinate at room temperature, turning occasionally, at least 30 minutes.
Prepare grill for medium-high heat; oil grate. Remove pork chops from marinade and pat dry. Season with salt and pepper. Grill, turning occasionally, until charred and cooked through, 6–8 minutes. Transfer to a platter and let rest 5 minutes.
Meanwhile, season jicama with salt and grill until lightly charred, about 3 minutes per side. Cut into bite-size pieces and toss in a large bowl with mustard greens, basil, and remaining 3 tablespoons oil and 2 tablespoons vinegar; season with salt and pepper.
Taste reserved marinade and season with salt, if needed. Serve pork chops with slaw alongside and marinade for drizzling over.