1.I think that there are so many common names in my country as María, Lucía, Laura, Antonio, Francisco or Javier.
2.Yes, It is.
3.No. My family name, Javier, is originative from Euskera language and literally means "New house", so It does not say nothing about my family.
4. As I answer above, my name just means "New house. About names in my country which refer to trade or profession I think that It is not usual, maybe the second name, but not sure at all.
5. I think that in Spain is not too popular use names from other countries although we are starting to hear names as "William" or "Kevin".
6. Here we usually use the first name from the beginning except if at the moment of introduce the other person tell you directly his short name or nickname.
7. It is not so common, we could do it but usually this form is used to made a joke or in a very formal conversation.
8. In my language, specifically in Spain, we usually use diminutives of words that commonly have bad meanings as "ratita" (little rat), "gordito"(faty), "tontito"(silly), etc.