Cut the tuna into 1/4-inch dice and place it in a very large bowl. In a separate bowl, combine the olive oil, lime zest, lime juice, wasabi, soy sauce, hot red pepper sauce, salt, and pepper. Pour over the tuna, add the scallions and jalapeno, and mix well. Cut the avocados in half, remove the seed, and peel. Cut the avocados into 1/4-inch dice. Carefully mix the avocado into the tuna mixture. Add the toasted sesame seeds, if using, and season to taste. Allow the mixture to sit in the refrigerator for at least 1 hour for the flavors to blend. Serve on crackers.