'It is hard for me to understand why she feels the need to make this situation so difficult, she goes out of her way to do and say things that will change his feelings and his relationship with any of us for the worse. She has been married to her husband for almost 13yrs and they have two kids of their own a beautiful home, and she still does these things. We never bother her or talk bad about her, or argue with her and she still does this nonsense.'
Let me see if I can put some perspective on it......it's because she HATES your
DH more than she LOVES your
SS. It's because regardless of what her life might be like now, she still holds a grudge against your DH and your SS is the most convenient tool to get back at him (and you by association). It's because she perceives this so-called 'pain' associated with your DH (and you) and she wants you both to hurt more than she does. It's because she's vindictive and spiteful and basically a school yard bully.
Your SS's behavior is a product of that hate. And that hate is so blinding to her that she cannot possibly realize what kind of damage it is doing to her own son. This child is caught squarely in the middle and his behavior is a reaction to that, along with the BS that she's purposely feeding him about your family. I know that it is difficult, but you really need to see the behavior for what it truly is...a cry for help. As 4honor said from experience, letting this go could cause even more serious problems down the road.
I know that an inclination would be to limit the time that he spends with you...and at times that may be the wisest choice, depending on what's going on. But keep in mind this: it won't change what he is becoming, thanks to his mother. She will see that as a victory on her part and up the ante, to the point that I wouldn't be surprised if she would eventually try to eliminate your DH from his life completely. In fact, that may be her plan all along. Just keep in mind that even if this were to happen, your SS's problems will still only get worse, not better. This poor kid is in a lose-lose situation right now. And he really needs an adult he can trust on his side. I imagine he has no idea why he's angry, just that he is. And even if he does know, it would be very difficult for him to voice it.
I truly feel sorry for this child.....he needs all the help, love, and support he can get right now. And I hate to be blunt about this, but there's no other way to say it: Your DH
must spend more time with him...if for nothing else but to lessen the pain this child is going through. He NEEDS his father right now, more than ever. And your DH should be bending over backwards to make that happen. The alternatives are NOT favorable: worsening behavior, assaulting your children, staying with
BM full time so that the mind-poisoning can continue full-blown, psychological problems that require treatment (do you honestly think BM would get him the help if he needed it?), or (heaven forbid) juvenile delinquency or worse. As I see it, that's the writing on the wall.......