In case you didn't notice, Facebook, Google and Twitter are based in California. So the law does apply to them.
http://news.nationalgeographic.com/news/2007/04/070420-extinctions.html Other researchers found that time periods Earth is exposed to large amounts of cosmic rays is correlated with mass extinction events. This is a possible explanation.
This is simply not true. Companies do not usually like to hire physicists, certainly not particle physicists. It is just not widely applicable to industry. Engineers are preferred. That's why there are not many jobs for them.
Why do you expect your real salary to increase without bound? If your labor produces value X you will be compensated in relation to that. You don't magically become more and more productive with time. After 15 years, more experience just doesn't increase productivity that much.
You have very specific and excellent advice for students starting out in grad school and I find your experience really interesting. I expect this to be useful to me in the years ahead. Would you mind telling more about your general experiences of grad school and afterwards? What kind of mathematical work do you do? (I am beginning grad student in applied math.)