1. To make a trade: my life for my dad's back when he got the cancer. I'd take the cancer and the heart condition and the eventual death, I'd want to take that all. He was worth more to those around him than I ever will be, he was loved, of use to others, of value to society and I loved him so much I would do anything to have him back. The added side effect would be that my family would only have to take care of one loser (their words, not mine) rather than two.
2. More of a curse than anything else, a curse of justice. I would like everyone who hurts others to themselves feel the pain they caused others as intensely as their victims do. It would make the world much more interesting. Admittedly I'd not be around to see it, but it seemed less selfish a wish than 'I hope this entire pathetic race dies in fire'.
3. I dunno. Maybe like happy ending for anyone suffering? I just can't seem to think of anything nice to wish for the rest of the world, most of them already have so much, appreciate it so little and have so much contempt for anyone who wants only the same, for them to get even more seems wholly unjust.