What I wanted to do was to caution you about your s12's 'preaching' to your W. Granted, I don't have all the details, so understand that these comments may be moot if circumstances are otherwise.
You need to make absolutely sure that your S understands that he needs to respect his mother, even if she is acting inappropriately. The danger here is not only the fostering of a 'holier than thou' spirit, but also the sin of disrespect of a parent.
It is only by God's grace that we are not in the position of our spouses. Take Amy for instance. She was there herself.
Your S is only twelve and while it is a wonderful thing that this situation has him studying the scriptures(look for blessings where you can find them), he should be studying those that pertain to him loving and respecting his mother and his personal behaviour(1 Cor 13 comes to mind), not for what he can find out about his mother's actions. This was the sin of the Pharasees, and Jesus had harsh words for them(brood of vipers, anyone?). I will not discount the comment that you felt this weighed on her heart, but the end should not justify the means. Your son has no right to be lecturing his mother, even if it is scriptural(IMHO). It will only go bad.
If someone wants to minister to her, they will have to LISTEN to her, walk with her, love her, and be there with her when God does break through to offer support and hope. This is not your S's role. His role is to show obedience and love. Help him to understand that your W is God's project, not his.
My opinion is you should be protecting your W from this type of attack from your S, and teaching your S at the same time what it means to respect someone God has placed over you even though you don't approve of their actions.
I Peter 2
13Submit yourselves for the Lord's sake to every authority instituted among men: whether to the king, as the supreme authority, 14or to governors, who are sent by him to punish those who do wrong and to commend those who do right. 15For it is God's will that by doing good you should silence the ignorant talk of foolish men. 16Live as free men, but do not use your freedom as a cover-up for evil; live as servants of God. 17Show proper respect to everyone: Love the brotherhood of believers, fear God, honor the king. 18Slaves, submit yourselves to your masters with all respect, not only to those who are good and considerate, but also to those who are harsh. 19For it is commendable if a man bears up under the pain of unjust suffering because he is conscious of God. 20But how is it to your credit if you receive a beating for doing wrong and endure it? But if you suffer for doing good and you endure it, this is commendable before God. 21To this you were called, because Christ suffered for you, leaving you an example, that you should follow in his steps. 22"He committed no sin, and no deceit was found in his mouth." 23When they hurled their insults at him, he did not retaliate; when he suffered, he made no threats. Instead, he entrusted himself to him who judges justly. 24He himself bore our sins in his body on the tree, so that we might die to sins and live for righteousness; by his wounds you have been healed. 25For you were like sheep going astray, but now you have returned to the Shepherd and Overseer of your souls.
Ephesians 6: 1Children, obey your parents in the Lord, for this is right. 2"Honor your father and mother"--which is the first commandment with a promise--3"that it may go well with you and that you may enjoy long life on the earth." 4Fathers, do not exasperate your children; instead, bring them up in the training and instruction of the Lord.
I don't throw this out off-the-cuff. I have a D14 in a similar situation. This is an incredible opportunity for you to instruct your S in the beauty of unconditional love, and show him how amazing God's love is for us:
Romans 5: 8But God demonstrates his own love for us in this: While we were still sinners, Christ died for us.
