1. You can find someone to rent from on the rent/trade board. Be aware, however, you're likely to be asked to pay for your whole reservation up front, or at least a chunk much larger than a deposit.
2. In the navigation bar above, there's a
DVC tab, go there and you'll find the
point charts.
3. Owners at each resort can book their home resort 11 months out, everyone can book any resort at seven months out. You're much better off securing the rental during the 11-month window. Especially if you want Aulani.
4. No maximum for point rentals. You just have to find an owner willing to rent that many points.