Questions for constructing Aquasport 52 partial in-ground

[JaceTheAce]

We purchased an Aquasport 52 18' round 52" pool and are planning on installing it 3ft in-ground. We are having our landscaper excavate the hole and he will be leveling the bottom of the hole with 2" road base that is power-compacted with a thumper. Our soil is not clay, but it's not sandy loam either - it's an ancient flood plain so the soil has a lot of sand but is also very rocky. The soil is quite "hard" and difficult to dig with a hand shovel.

Questions about constructing our Aquasport 52:
1) The Aquasport manual mentions treating the outside of the pool wall so the soil doesn't accelerate corrosion. Do we need to treat the outside walls below grade with something like Ames Blue Max?

2) Aquasport 52 is designed for partial in-ground installation. Can I backfill before adding water? If I have to fill it with water before backfilling, then in 10 years when I drain it to change the liner, is it going to collapse?

3) The pool floor will be 2" power-compacted road base. The Aquasport manual recommends using patio blocks under every buttress. Given that we're using a compacted base, are these really necessary?

4) I'm considering putting 1" hard foam board insulation on the outside of the pool walls before backfilling to help keep the water warm. Will this work?