1) Don't know.
2) Amphetamines or ephedrine definitely make you more alert and motivated. But they have many side effects and using them for exercising will probably damage your heart.
3) I discovered that Zolpidem ups my creativity quite a bit. Problem is, it's so sedating that you really have to fight to stay awake. It's a sleeping pill, after all. Also there is a bit of hangover and after reading some papers I'm very skeptical of benzos and Z-drugs like Zolpidem. They seem to increase the risk of infection (actually shown through a double-blind study) and people taking only 0-18 hypnotics per year have a ~4 times higher mortality. Sure, it's only correlational data, but still. Then there is of course the classical psychedelic: LSD. I haven't tried that many psychedelics but LSD is my favorite. Your thought processes are very different and you'll see the world with different eyes but can still function quite normally - provided the dose is not too high- and can write and talk like normal people.
(Apropos, of course this comment is fictional in nature and I don't consume illegal drugs. They are illegal, after all.)
It didn't need to be. It was merely describing chemicals and had no mention of you using them. Theoretical seems to be the appropriate term.
We operate like this: the "overseer process" tells the brain, using blunt instruments like chemicals, that we need to find something to eat, somewhere to sleep or someone to mate with. Then the brain follows orders. Unfortunately the orders we receive from the "overseer" are often wrong, even though they were right in the ancestral environment. It seems the easiest way to improve humans isn't to augment their brains - it's to send them better orders, e.g. using drugs. Here's a list of fantasy brain-affecting drugs that I would find useful, even though they don't seem to do anything complicated except affecting "overseer" chemistry:
1) A drug against unrequited love, aka "infatuation" or 'limerence".
2) A drug that makes you become restless and want to exercise.
3) A drug that puts you in the state of random creativity that you normally experience just before falling asleep.
4) A drug that puts you in the optimal PUA "state".
5) A drug that boosts your feeling of curiosity. Must be great for doing math or science.
Anything else?