I cannot answer to those questions because a part of the answer is very confidential and private, but also because I am not an expert about this topic.
Salaries can variate from country to country, in USA it is different from Europe, and within those countries there are big differences if you are working in the South or in the North.
Coroflot.com just published a designer salary survey worldwide and it works simply participating in anonimous way to their web tool survey, then they collect all the infos and started to give a picture about how designers are gaining per year according to their job role career and company size.
I find it extremely interesting for all students looking for this infos, but also for professionals that feel like changing and try to understand how much they could earn more and with what kind of benefits.
To discover and to participate (if you are a professional designer) click: Designer Salary Survey