Inappropriate emails sent on government computers

I just discovered (On January 4th 2012) that a Government contractor employee and my husband have been sending emails back and forth and expressing inappropriate messages to each other. I do not have all the emails, but my husband and the other woman have both confessed via email and on the telephone to me but will not provide all of the emails which were sent between the year 2000 and ended in the year 2009. They both also deny that they ever met and claim that their exchanges were limited to inappropriate emails. It has destroyed my marriage. The woman (who works for a very large government contractor) used her work email during working hours to communicate with my husband on his Yahoo account.She was the also allegedly the person who made the first contact. My husband is a Government employee working for a major branch of the government. The communications took place during work hours while each party was working, but my husband told me that she sent emails to his yahoo account and they were accessed through him logging onto yahoo using his government computer and home computer and laptop. Are government contractors and government agencies partly responsible for allowing this to go on and for not monitoring the emails which were inappropriate and were exchanged during working hours? I believe that the government agency and the contractor bear some responsibility for allowing this to go on for such a long span of time. The woman has emailed me that if I report her to her agency and if she loses her job as a result, she will sue me for lost wages? Is it likely that she would be successful in sueing me? I think I can sue her, the government contractor, the government and my husband. I am concerned though, that if I report them, I will be cutting off my own foot as we have three children in college and although I am a working professional, our income is mostly from my husband. I live in Virginia and the woman lives in Florida. What rights do I have? Because I am going to divorce my husband, I am going to now incur many expenses but the worst part is the emotional devastation that has been place upon my children and myself. I just celebrated my 25th wedding anniversary with my husband and my marriage was a loving marriage. When I found out, I did read some of the emails where they both exchanged emails back and forth writing about being in each others arms and loving each other. But my husband deleted the emails and then his email acccount and the other woman has not provided the emails to me to prove that they did not meet. But just knowing that they told each other things that should have only been reserved to say to the other woman's husband and to me, it is enough for me to feel betrayed and completely devastated. I do not know what to do. Do you have any advice for me? Thank you