1.That's fairly high compression, especially to be supercharged - LOTS of honda guys would run a similar setup, but ideally you want to be a point or three lower in compression.
2. GZE pistons will fit fine. They 8.9:1 ones are the way to go. Since you already have aftermarket pistons, i wouldn't buy your new gze pistons until you see an engine builder, and they tell you what bore size you're currently on (there's a good change you're already 0.5mm/20 thou oversize), and whether or not the previous bore job was done well or not.
3. For rings, just buy the toyota rings meant for the pistons - again, wait until you can confirm bore size.
4. With the strong aus-usd conversion rate, i'd be buying from the states. PASS racing sell them for $450 with rings, there might be cheaper places though.
5. Now that they're used? All depends on condition, and what people are willing to pay for them - i would say anywhere from 150-350