We all just want our marriage to work. We all wait for things to change. 

It's tough.. I think a lot of it has to do with the fact that it's hard to let go of a bad decision.. because we have invested so much into it.  We also gert wrapped up into the ideal where we see what it "could be if only".. but the "if only" is part of it..so it is what it is.. but it's hard to walk away from our dream.  Failure.. the fact that we didn't see the red flags.. and we own part of the dysfunction.. so leaving means we failed too.  Wanting people to like us.... if we leave.. they will hate us.  

And.. finally comfort.. leaving is hard.. and as frustrating as it is living with him having that kind of communication with his EX.. leaving means finding a place to live.. living with potentially fewer resources.. having to do it all alone.  

Then there is fear of unknow.. of being alone.. "forever".. I mean.. at this point.. you should never be with someone with minor kids.. because even "normal" levels of communication with an ex are your trigger now.  You can't stand it even when it's something that should be normal for parents of kids to discuss things about their joint kids.. The fact your husband has few boundaries.. means your boundary is a 20 foot high wall.. so it has kind of ruined you for a large portion of potential partners.. 

But.. there are worse things than being alone.. and if you think what you are dealing with IS worse.. you know the ultimate step you have to take.. 

You will leave when you're finally ready. It can take a long time to accept that nothing is going to improve.

I stayed with my XH1 for 26 years because we had a family and financial entanglements.

I stayed with my XH2 for 4.5 years because of a trauma bond from abuse.

I stayed with my XBF for 4.5 years because I loved him, his mom died and he just wasn't HORRIBLE. I chose to wait until I was sure that he wasn't able to be the kind of partner I wanted and deserved, and I had to decide that being on my own was better than being with someone who was on the fence about me and struggled to give me the bare minimum.

You will leave when you're ready.

If you have brought up your concerns about the over communication & he continues to do so, he's not going to change. 

I had to have a similar conversation with DH a few years ago. The hour long phone calls re-hashing the past, BM wanting to "sit down" together with DH to talk, etc. were all excessive & IMO inappropriate. DH was clueless to most of it wasn't really seeing how it was affecting me. I can wholeheartedly say DH did change his actions... honestly if he hadn't changed, I'm not sure if I would have been able to stay. It was so draining and exhausting I don't think I could have stayed. 

Him not following the basic " SO will not put up the boundaries with BM and kids " has to be a deal breaker.  You cant live with this interference in your life / relationship.. The therapist told him what he's doing is wrong  But he doesn't care / nor left the old relationship.  Being disrespectful to you.   Really time to tell him to change or else.  And start making an exit plan .  This may never change.  You will be 80 yo and BM will still be texting wanting him to find her teeth    No way to live .

I insisted that this type of nonsense end with my SO  I got it's for the kids  exchuse  I say get back together with him, for the kids .  I would not live that way.

Sound like he wants to please you and the therapist by agreeing to set some boundaries with BM. But he's not yet been willing to make that hard change. Status quo works for HIM.

I would find a calm time to ask him. No accusations, no tears, no anger. Go with curiosity. Where does his hesitation come from, and what does he need to move forward.

That kind of discussion works incredibly well with DH. Not so much my ex, who couldn't get past his own anger to actually do anything. Until I actually left him. Then the begging started. 

I had the exact same issue with my ex (lack of boundaries with ex wife and kids) and it heavily disturbed my peace because his kids ended up living in "our" home (which he considered his kids home) every.mfing.weekend.and.holiday

When I told him to cut this Disneyland bullsh*t because that crap disturbed my peace in the home I paid bills in .... he simply doubled down, argued with me like a b*tch in favor of his conniving exwife and unruly kids, then had the gall to complain I wasn't f*cking him lol

Let me say this - If these kids aren't special needs, breastfeeding, or terminally ill then they are not the center of my life ... my spouse / marriage is (IF I married well) first then the kids. 
 

Any man who puts his former family ahead of his new spouse doesn't need to be married and is just using you for free labor and whatever else you willingly sacrifice. 
 

Men with multiple obligations have to learn how to balance it all but we see a lot of them favoring their exes and kids from previous marriages to the point it's like they struggle to move on and probably should have stayed with their exes or stayed single till their kids are grown. 
 

Only you can decide what your threshold is for dealing with Disneyland type dads. Me personally, dude would have to bank multiple 7 figures for me to deal with a c*nt ex wife and no-home training skids .... 

May sound cold but I'll NEVER do step parenting for free out of the kindness of my heart because these people will take advantage, drain tf out of you, nothing is ever enough and you're always at fault 

Men with heavy baggage need to be compensating or else it's not worth staying with them self sacrificing till you have nothing but complaints, resentment, and regrets 

We all start a marriage with the fantasy.  Hazy framed light footed romps through the beautiful meadow in a life together.  Or whatever fits our individual fantasy picture of a life with our mate.

Then... reality.  The draw of the fantasy clouds the view of reality.

It certainly did for me in my first marriage.  I knew on the wedding night that it was over.  I should have initiated an annulment on Monday after the Saturday event of the season wedding.  I did not have the courage or maturity to do that.

So, I went all in to make it work.  The problem was that my XW was not in at all. All in from partner does not work with not in at all from the other.  So, I pursued a path of insanity experiecing the same things over and over again while hoping for a different result.

In hindsight, I owe my XW a debt of gratitude for leaving.  It likely would have taken me far longer to end it.

I will never again do that to myself.  Fortunately, I have won the marriage lottery the second time I played.  Through there are no guarantees, this one is looking good so far.

I agree with the perspective that your SO is doing exactly what he always has and that is what he will continue to do. He sees the therapist because you expect him to.  But, the difficulty is not in the therapy, it is in changing one's historic and chosen behaviors.

Sadly, you are right. This will not end until you end it and the only likely solution is... to end it.  BM is not going away. Ever.  SS is not going away. Ever.  The odds are overwhelming that Daddy will never do what needs to be done to prioritize you or your marriage.

I understand and have lived not taking action when that action is painful, will likely fail, and will untimately end a marriage.  I will never again sacrifice me for a mate who does not make me as much of a priority as they make themselves. For damned sure, I will never tolerate my mate prioritizing anyone or anything over me and the relationship we share.

Doing nothing, changes nothing. Never forget that.

Take care of you.