Your dh should be addressing this with B&M or have your lawyer file harasssment charges. It is not a child’s responsibility to call BM out. He is a child and that’s still his mom even if she is apiece of shit. 

that's a lot to put on a child. 

Yes, I agree - don't put this on him. I guarantee that BM is filling his head with nonsense about how DH stole him away from her and how he's abusive and scary, and Mommy loves him the best of all and will do everything she can to get him away from that scary monster - DH.  But deep down, SS fears that if he stands up to her, he will lose her for good. He may in fact know she's the problem, but asking him to stand up for DH to her is too much to ask.

Next time - tell the police to inform BM that SS is fine and will call her the next day, as stated. This is just another way for BM to alienate SS.

This is a high conflict BM, and SS isn't either the problem or the solution.

I agree with everyone else, your DH needs to be the one addressing this with his ex. His mum being a POS isn’t your SS’s fault, and no matter what she’s still his mum. He’ll talk with her when he’s ready, but as far as addressing the cops being called, expecting your SS to address it with his mother is inappropriate & completely unfair. The kid is only 12 years old, and, again, it’s not his fault that she’s a POS. If you want to blame anyone for that, you should blame your DH for knocking her up in the first place.

The adults, meaning DH and BM need to deal with this issue not ss12. He is a child and should not be put in the middle of this high drama. You two are coaching him about how to talk to his mother and telling him "you need to call your mom right now and tell her to stop calling the cops on your dad." Nope, dad should have called. No family court would condone this kind of behavior towards a child and making him the go between. Also DH was withholding communication with ss from BM. If ss and BM talk on the phone every night then that is in the court order or is the status quo and needs to continue or your DH is the one in violation. 

Yes BM did some terrible things in the past, hence DH has custody. Technically, all that custody means is that DH gets to make the legal decisions for ss. It also gives DH the responsibility to facilitate a positive relationship between ss and his mother. If DH cannot or is unwilling to do this then custody can be reversed.  Custody is not some power trip that allows one parent to remove the other parent from the childs life. Even 'unfit' parents have some rights to visitation and commucation with their children.  

The boyfriend issue;  "We encourage him to say "mom I was upset bc I found out about your boyfriend".  I highly doubt the kid had any idea of the boyfriends past until you two brought it up to him.  Again, this is an issue for the adults to deal with not for SS to confront his mother about.  If DH is truly worried about this guy then he needs to address the issue through the police and courts. 

OP, I would encourage you to stay completely out of this. DH needs to parent his own son and he needs to deal with his ex. She may be all those things you said but the fact is that you DH chose to make a child with her so it's his responsibilty to deal with her.  

If this guy is a registered sex offender then why  can't you call the cops on him when SS is over there?  Give them all a taste of a cop visit. If SS comes at you expressing his feelings shut him down.  There are logical consequences for acting the way he does.   If BM is HC, she might lose her mind on the cops. I say , play a little tougher,  give her some rope and see if she hangs herself. What more can you lose?  

This is a parental alienation situation, even though he sees BM infrequently. My SS was the same way, he couldn't stand up to BM at all, even though he complained about her to us.

When he was 15, he stopped coming over to our home at all and stopped speaking to DH. DH didn't fight it because we'd already spent ungodly amounts of money in court and it was harmful to SS to keep dragging him into court where he lied for BM.

Your SS will probably do something similar without you suggesting it, when he hits 14 or 15.

SS came back into our lives at 18.5 but he's a hot mess and the damage is done.

Unfortunately it is not uncommon for kids to refuse to 'dime out' a awful parent. WE (you, me and others) know it, we see how unstable they are and yet, the kid remains silent

People who call cps or the police with lies are trailer trash...jmo.

I cant say I don't blame you for being very p-od. It happens. Dont be hard on yourself. ok?

 I also say, maybe you should call a welfare check to make 100percent sure the perp is not at bm's house next 'visit'.

Like you , I would not want my bio's around this mess either.

(((HUGS)))))) I am so sorry. What your going thru it is very very stressful.

You are welcome,,,I do get it.

IF your concerned about retaliation, discuss that with police too.

The concern that remains IS, is about the perp.  Which by the way has been there before. SHE creates the problem not you. Women like this usually twist everything around (mental health problem)--and project it back to YOUS cause this problem, its not meeeeeeeeeee,,it's THEMMMMM, I am worried about MYYYYYY son at his DADS house so I call the police on THEMMMM..

Keep kid focused, kid concern, perp concerned, revolving door of low life dudes in her house.

(((SORRYYYYY)))

If you are worried about retaliation, bone up on your trespassing laws, what it takes to get a protection order and any other legal answers you might need. The better armed you are going into this the better. In the ART of War you need to know your opponent's weaknesses and how to keep yourself protected. Years ago there was a man on here (Draco) who did a series on the book and how it applies to step life. If you step back, take a hard look at BM's behaviors and you will find/see her patterns. Use those against her.  I had a nightmare BM to deal once upon a time. Once she learned I was not to be F'd with she changed her behaviors.  Stand up for yourself and your bios.  No matter what DH thinks.  My DH was scared then relieved someone finally gave BM her 2x4 upside the head. She didn't like the cops showing up at her house and the neighbors saw.  IDGAF.