Place pork into the bottom of a 6 quart crock pot then season generously with garlic salt on all sides. Add the can of chopped pineapple including the juices, 1/2 cup BBQ sauce, and sliced onion. Mix slightly then cover and cook on low for 7-9 hours, or until meat shreds easily. Shred then mix 2 cups pork with remaining 1/2 cup BBQ sauce (there will be extra pork - it freezes well!) Discard cooking liquid.
Meanwhile, preheat oven to 400 degrees then stack tortillas and cut them into quarters with a sharp knife. Place wedges onto two baking sheets leaving at least 1/4" between each wedge. Spray tops with nonstick spray or mist with extra virgin oil then season with salt. Bake, rotating pans halfway through, for 8-10 minutes or until golden brown around the edges. Chips will crisp as they cool. (Can be made ahead of time - cool completely then store in an airtight container.)
Layer half the chips into the bottom of a 12" oven-proof skillet then top with half the pork, cheese, pineapple, and chopped red onion. Repeat layers one more time then bake for 7-10 minutes, or until cheese is melted. Alternatively you could use a baking sheet instead of a skillet.
While nachos are baking, combine avocados, garlic, lime juice, and salt in a bowl. Smash with a potato smasher or fork until desired consistency is reached. Fold in cilantro and pineapple tidbits. Serve Pineapple Guacamole with nachos, along with extra BBQ sauce for dipping.
Notes
Feel free to use 24 tortilla chips from a bag instead of baking your own tortilla chips.
Pineapple tidbits are used twice - you'll need one, 8oz can for this entire recipe.
Nutrition is calculated with 2 cups of shredded pork + 1/2 cup barbecue sauce, with all of the chips, guacamole, and "for nachos" ingredients.