Obviously I'm taking a U.S.-centric viewpoint here....
1/ Well, heck, if I'm helping spend the entire world's money, might as well spend a little of it on me. I don't need much salary, maybe $250,000 or so, but that's because I am able to expense just about everything.
2/ A non-traditional succession constitutional monarchy. On the assumption that I know best, I can't be voted out, but there are clear guidelines by which I must abide (to avoid the "do it or I kill you" sorts of activities). And I'm not interested in having my offspring inherit the world (literally) so I get to choose who comes after me when I quit or die.
3/ In order: 16,16, none, 21, 16.
4/ Elimination of most classes of victimless crime, especially drug-related. Imposition of extreme penalties for persons who perform criminal acts under mood- or mind-altering substances. (i.e. toke all you want, but if you get wasted and hurt someone, you're toast.) Elimination of public education, to be replaced by private schooling. (Market forces, which have already driven U.S. colleges to the top of the heap, should take care of improving basic education as well.) The money saved by eliminating public education will be funneled into vouchers and financial aid for people who need it in the new education economy. For local government, voting rights come only after military duty and successful completion of advanced civics courses.
5/ Taking a deep breath right after the swearing-in ceremony.