Hi Teetor,
In regard to tile and concrete the main concerns addressed by manufacturers are crack movement and slab movement, normal moisture passing through doesn't seem to be a concern. Ditra and products like that have been created for dealing with concrete, but vapor barriers don't seem to play any part in tile laying, unlike laminate flooring that is made of wood and causes the problem because it absorbs the moisture, tile doesn't absorb moisture and doesn't expand. No manufacturers nor the Tile Council of America recommend any type of vapor barriers for tile. Tile releasing or grout cracking is almost always due to the substrate moving beneath tile. If I got you right, you said the slab under your tile moved 2 inches? If that is the case the issue is slab movement and not moisture passing into your tile. Like I said tile doesn't absorb water and expand so the tile is never at fault, it is always the substrate. While it seems you have found a combination of thinset and sealer that isn't reacting negatively to each other, I don't believe you are actually gaining anything from it.