Can I contact the author of a paper for questions, even if I've never studied over high school?
About your questions:

1) If you want you can link the Wikipedia article or make a small summary explaining your thoughts, usually Professors or researchers do not have too much time to read long emails; so try to keep it up simply

2) explained before

3) It is nothing bad that you point to the other papers of consequence Z, if he knows about them he will tell it straightforward

In conclusion, do not feel bad that you did not have any formal education. Just address to the researcher in a respectful manner and tell him/her that you are interested about his job. You do not need to send your CV or a motivation letter just for asking something, but beware, you can or you cannot get an answer (usually depends how much interested of free time the researcher you are appointing has)

Good luck!