It sounds to me like you've put extraordinary effort into your marriage. I commend you on that. My thoughts about this is you'll have to weigh everything very carefully to make whatever decision you feel is best for yourself.
The way I see your husband's situation is that he's a person with an addiction problem. Just like some people are addicted to drugs, he seems to be addicted to the feelings he gets from these relationships.
I think you understand this and that's why you are probably able to handle this situation so well. You're not taking it personal. Which is good.
As far as where to go you'll have to determine that. In the meantime I do agree your husband needs to go into some very good psychotherapy. Maybe even some type of cognitive behavioral therapy...
There is no arriving, ever. It is all a continual becoming.
