I'm so sorry for the trials you are suffering. I think we need to stop victim-blaming here, and simply show Christian love rather than judgment.
Which, Mr. John, is the same advice I would give you concerning your gay best friend. Of the problems you have mentioned in the OP, that is the one I could best deal with if I were in your place. I think what one of the members is trying to say, but it may be coming out wrong, is that it isn't for us to *make* other people live Christian lives. The only thing we can do is model it for them, as Christ models it for us. I would advise continuing to treat your friend as you always have. Whatever you do, don't misrepresent Christ's love to him.
As for your family, Paul counseled the church to let unbelieving spouses depart if they wish to do so, and not be under bondage. 1 Corinthians 7:15. I can't say whether or not your wife is unbelieving, but using drugs, having an affair, and abandoning your family are generally not things most believers would do.
You're grieving the loss, and so is your daughter. I have very little advice for you except to pray, also remembering to pray for those who have hurt you. This would include your wife *and* those who led her astray. Set an example for your daughter, and try to be patient. Her world, like yours, has crumbled out from under her, and she is going to be squirrelly. So will you. Lean on Christ and show her how to draw closer to Him when things go wrong.