I have a fiberglass pool, and the pool is level. I would go back to the people that excavated it, and find out what went wrong. I never heard of "building a tile wall to compensate" that's rediculous! I would make sure it is fixed before you do anything around it - even if you have to get it raised by a crane again - because if you don't fix it now - you will never be able to fix it, and a good fiberglass pool should last a lifetime. I have mine for 7 years, and it is just as good as the first year I had it put in. Don't let them talk you out of having it fixed. Of course this is my own opinion, I don't know the leagal aspects of what you can do. Best of luck, and stick to your guns!