Ibaka is even younger, but he doesn't really play SF. Still, he would certainly be a nice addition.
Getting Dwight isn't the only way to make Deron stay, however it is the surest option.
Yes, about 4 years younger.
Paul is a beast. I don't think his injuries are bad enough to take him out of the elite pg category. I'd definitely take Paul over Westbrook now, but Westbrook would be a very nice as well.
The nets have a lot of holes to fill, but they have the resources to fill those holes. They just need to use those resources wisely.