Thanks BTDG ( your nick describes me well )
1) At 52" the pool wall is an acceptable barrier.
2) The cheapest pools do sport 20 mil liners.
3) I haven't seen anything yet 2" wide. The cheapest I've seen are around 6".
4) How thick should I expect, I haven't seen alot about wall thickness - coatings, corrugation, style, but not thickness.