What can be done?

My STBX (of 22 yrs)left our home 3 weeks ago. He is now living at another residence in the same state with his mistress. I too, feel like I have a case for Alienation of Affection but, I don’t know the legality of it. If I can file a case I will. They worked together for six months before he left, I think because people were beginning to talk. I have evidence that it began before he left or shortly after. I have found lots of emails with loads of details. We have two teenagers in the home. He sometimes doesn’t even contact them. I presented him with a SA and he just laughed if off, now we will probably have to go to court. What can I legally do if he won’t sign the SA and what do I need to file A of A case?