Wow, long post, but really good. You've really been thinking about this a lot, huh?
As far as smarts being unimportant vs, working hard, I do think it's a combination of the two. I know plenty of people who work hard doing backbreaking labor at construction site, factories, in office buildings as cleaners, etc., but they don't work smart. They choose dead end jobs or they just bumble through a job just well enough to sneak under the radar.
Success is a mix of vision (say smarts) and discipline (like hard work). Some people are so good at one area that they can make up for a deficit in another area, but these people are few and far between.
You can make a list of 20, 30 or 100 problems, but at the end of the day they always fall into one of the two categories: vision or mastery.