Unfortunately, while correct for the most part, you are not thinking things thoroughly enough so allow me to enlighten you. First off, you are right that higher educated people are constantly less and less likely to have kids and/or families (eg: Japanese Women) and the less educated people may even hold having a family as their goal in life. With the progression of our world many people have come to believe that family is just a burden, not a bliss, thus avoiding starting one. THAT is plain stupidity at it's finest. Now, what you are wrong about in your first point is that natural selection doesn't function as it should anymore. Natural selection means this, the environment and the world around us change, if you can adjust, you will survive, if not you are dead meat.
Moving on, true, overpopulation DOES cause a lot of problems, if not most, so I totally agree with you on that. Stupid people just keep breeding and multiplying their numbers, then they intentionally or unintentionally ruin the world. However, what you said, that fewer people would mean less problems, while mostly true, it depends on WHO the people left are. Are they stupid or not? Imagine a world where only the stupid ones have survived! Try to imagine humanity's future then!
Finally, nature will destroy humanity for sure, the question that stands is: will humanity go extinct by themselves or not? Also, the solar flames you mentioned no longer affect electronic devices as much as they did, nowadays, they simply mess up with the microprocessor clocks (too much to explain), meaning that most simple devices won't be affected at all and those that will, may not malfunction too much or may just explode (or so many different types of malfunction, too many to list).