Whisk together all the ingredients for the pork marinade. Pour it into a gallon ziploc bag along with the pork chunks. Marinate at least 4 hours but preferably overnight or up to 24 hours. Stir together the tzatziki ingredients and set aside in the refrigerator. Thread the pork chunks onto skewers, shaking off excess marinade. Grill until nicely charred and cooked through. While pork is cooking, assemble the salads. To serve, dress the salads with oil and vinegar. Top with souvlaki skewers and a blob of tzatziki for dipping. Make-ahead directions: Combine the pork and marinade. Freeze in a single large zipper bag (if you will thaw and cook the whole thing at once) or in individual portions in zipper sandwich bags (to thaw individual portions). Salad cannot be frozen; make it before serving, or a couple of days beforehand.