If you mean "gaps in my education" or "basic things that I don't quite understand", you could try studying some high-quality texts. Look for books written by extremely smart people who are trying to explain the ideas rather than taking you through the standard topics. Hamming's books on probability and signal processing and Strang's books on linear algebra and applied math come to mind.
Alternatively if you're really interested in intuition, you could also look at the Math Olympiads. Pick a problem, beat your head on it, finally look at the solution, repeat. There are web sites and prep books.
Not just nylon ropes, but multi-fall ropes: in the early 70's, we didn't trust a rope after it had taken a hard fall. You can't learn a big-wall route if you have to retire your rope after every long fall.
From personal experience, I can tell you that $6K/month is not exclusively a Silicon-Valley phenomenon.
Basically you cover it with whatever SS, pension, savings, and other assets they have. When those don't cover it, you make compromises in quality of care, your finances, and your family's life.
Go read Ronald Coase's "The nature of the firm". And if your work _can_ be structured to minimize the transaction costs, you might as well go to a low-wage country rather than mess with a remote, medium-wage team. I worked with one company that had all of their engineering team in Pakistan. The SV-based VP engineering never saw his team face-to-face. They had a huge cost advantage.
With some exceptions such as siblings of current students, the schools are not strategic actors in the Amsterdam problem. If you meet the entrance requirements, you're eligible, and that's all the schools are allowed to say. In the stable marriage and the residency problems, both sides express preferences.
Back when DCVS was just becoming a thing, I started with darcs and rather liked its model. I soon discovered that darcs had a nasty problem of quietly accepting large binary files that it could not manage -- you only discovered that the file was too large when you needed a revert or something similar. This led me to give up on darcs, and I switched to git. I could have gone to mercurial, but it appeared too sane and not as exotic.
The U.S. was the dominant whaling country at the time of Moby Dick, but there is little in the book that assumes a knowledge of American history, culture, or literature. It's a candidate for "the great American novel" only because it was written by an American. I've read it more than once, and it strikes me as something completely original, not tied to the conventions or themes of literature of its time or country of origin. You may or may not like it, but "Americanness" won't be the reason.