prevailing wages for software engineer

I was hired by a big company on 2000, and they filed my h-1b on 2001. At that time I was a junior, and the previling wage they put on my h-1b is around 50k.
My salary is lower than that.
On 2002 I married my hu*****and. He works in same company as I. His 485 was filed
as pending. So I joined after.
After he got his green card, company adjusted his salary according to previling wage. 2005, Company renewed my h-1b, still same previling. I am 6-7 years software engineer,and since the company said my hu*****and sponsored me, so they will not adjust my salary.
Any body can help me answer the question?
1> What is the previling wage for 6 years software?
2> why the previling wage I searched on web are all 60k-70k for software
engineer, is company made some trick to INS?
3> Is that true company has the right not adjusted my salary?
4> If the H-1B prevailing salary I found is a lot higher than 50k, is that possible I sue the company to get the 5 years difference back?
5> Even though my salary is always lower than the prevailing in my h-1b, company said within %15 is OK, is that true?
Thanks for all information input!