Content theft - need some advice

[Darigaz]

I am going to lay out a scenario that is taking place in the hope that people can give me some insight.

A partner and I founded our forum 8 years ago on an older version of vBulletin. My partner had ftp access and gave ftp to one of our web masters. Said web master gave ftp to one of our community admins who said he wanted to do some clean up on the server (he made a mistake by not consulting with my partner and i), but instead the community member just stole the content and relocated to a new domain.

Another community member donated our vb4 license, but happens to be friends with the offending community member, and therefore switched the license over to the offending website. We have no problems buying a new license, thats not the issue.

The issue is...
1- They are using our custom design which we had designed for us. I can have the designer vouch for me as the original purchaser of the design
2- They are using our community name
3- They are using a duplicate of our website with all of our posts / threads that have cumulated over 8 years. Our content is our primary concern here.

My partner and I are the original owners of this content and we founded the community. The offending members were previously in the community playing admin roles and are actively attempting to steal members from our boards along with our content. We do not own an LLC under the community name, but we have the following proof of our ownership...
1-webarchive that shows we founded the community in 2004 and we can show dated posts and other archives that demonstrate we are the original founders/owners of the community. We are also listed as userID1 and userID2. We have plenty of content to prove that we were the original owners.
2- testimonies from our web designer who made the skin and from our custom coder (the offending parties are planning on changing the design/site name but keeping all of our content on their board)
3- testimonies from our current community members and past members who can vouch for us being the original owners, but the offending party also has some people who would vouch for them because they are a part of the faction as well.

Because it is a forum board, copyright laws seem to be slightly convoluted. What I am wondering is this...
- Do my partner and I have copyright to the content on our forum? In this sense, can we claim that the offending party is breaking copyright by stealing our content even though the content consists of peoples threads/posts?
- Do we have legal grounds to sue?
- What measures can we take before having to take a legal route, we would prefer not to spend money. But we have put nearly ten years into this project and would be willing to take this to court if we have a case.

I hope someone can bring insight into this situation. Also you can PM me and I can give you my skype information so we can talk about this further. Thanks