#1 I have never built an above ground pool, take this for what it's worth.
#2 The AG pool instructions I've read say to dig a level area to build the pool on undisturbed soil and not to build up or fill in.
#3 The sand goes inside the pool and is levelled after the pool is built, it is also used to build the cove.
There are people on this forum that have experience with this. I chimed in because it sounded a little like you were going to build the pool on sand - that could be disastrous.