I still am hesitant to judge this situation. The state of the marriage, whether your elders know what's going on - you may have explicated these things and I may have missed them, but they can be critical.
In general though, this situation invokes deep consideration into the general state of the church. The NT church was more or less a cohesive unit, despite its problems. When that cohesion was violated there were consequences, as the story of Ananias and Sapphira dramatically shows. Today it's not that way, and any church that takes a stand risks a defamation suit. Perilous times, indeed.
I would commend to you two chapters: 1Cor 5 and Matthew 18. In Matthew, the protocol is given for dealing with a sinning brother. In 1Cor, Paul deals with an openly sinning brother that hasn't been disciplined.
I wrote you in my letter not to associate with immoral people; I [did] not at all [mean] with the immoral people of this world, or with the covetous and swindlers, or with idolaters, for then you would have to go out of the world. But actually, I wrote to you not to associate with any so-called brother if he is an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler--not even to eat with such a one. For what have I to do with judging outsiders? Do you not judge those who are within [the church?] But those who are outside, God judges. REMOVE THE WICKED MAN FROM AMONG YOURSELVES. - 1Co 5:9-13
Sorry if I've missed this, but have you talked to the elders about this? You could bring it up in general terms without mentioning names, to ascertain what they think about situations like this.