MIL with BPD enmeshment help

[Overwhelmednow]

I don't even know where to start. When I feel we are making progress it takes two steps back.
Some back story, he rarely talked with his mother prior to us being together. Often spoke I'll of his mother, and I would be at her defence. I had no idea of her mental health, lack of boundaries, manipulations or lies at that point. I just knew she was a little quirky and none of her children had much to do with her. I started seeing the signs come out after we had a child and she began coming around way more. At one point telling my mom she was going to find a way to be at the birth, after being told no.

She has other grandkids that she has broken many "normal" boundaries with. At one point trying to pick one of them up from childcare after being told no, and losing the ability to ever babysit them. I don't think they have spoken clearly of this boundary, just avoid it from ever happening again. There are many instances thar came to that decision, not just that singular moment. She is often caught in lies, manipulation, and uses gifts as an alterior motive to get in the door. She has a history of going through men, moving around plenty, and never settling in one spot. Until now.
We recently moved, I left my entire support system. And she, without telling us, got a job and started renting here. This also means we will have to work together as we work in the same field. However, I will be her superior in this field. Making it extremely challenging as she is often fired for incompetence from previous jobs.
She mentioned buying a place a few months ago and I said we needed to make our boundaries clear. When she first came here it was to visit for a few weeks, then months, before ever getting a job. Often giving us money woo stories, and me being home with a baby was allowing full access as we likely wouldn't see her much once she moved onto the next place. Looking back this gave her a very unrealistic expectation of what living here would be.
We agreed expectations would be important but H always found excuses. It wasn't the right time, he wanted it to feel natural etc. It never happened. She has since bought a place and it caused a lot of tension between us. Again, I insisted boundaries would only be fair to her as her moving here was likely due to unrealistic expectations. Although we hadn't been making the same space and allowance for her visits once we realized it wasn't a quick visit. The boundaries were in my mind simple, healthy and normal. We are a busy family, (I have other children), we both work, and we are constantly running around for activities. Also mentioned we didn't have any intention of using her for childcare (we also have our reasons to not safely trust her with the kids, she cannot be trusted with animals let alone kids) He said she sounded upset and felt guilty. He then proceeded to take it out on me very negatively for days to follow. Calling me controlling and other quick remarks.
We saw her around town a few days after and everything was fine and normal. I pointed out how it was all normal, she was handling it well and how great it was. He then stated it didn't change how felt about doing it (guilty and mean). And again became negative with me.
I'm at a loss. I feel he is constantly on edge with her living here. He is always worried she is on the verge of a mental breakdown causing massive anxiety to him. He does not enjoy her company, but her best interest is far above his or our families best interest. He cannot tell her no, and if he does his behavior towards me changes even if I had no input on that no.
I know there is enmeshment happening, he was the only sibling left at home when his dad moved away. Leaving her to rely on him in unhealthy ways. Anytime she needs something she calls him, and since moving here it's often.
I have tried to explain how it's great to help but we also cannot be her go to contact for all needs/wants/rescuing. Her move here was full of expectations we have no intention to fill, but he is being pushed more and more to please her whims and wants.
The list really goes on and on of how she doesn't respect boundaries. She sees them as a challenge. Her behaviors can be very innaprotiate, trying to cuddle her adult son etc. It's just too much and I'm at my breaking point. I cannot live like this. My SIL doesn't talk to her at all because of her constant behavior. I don't want to get that far. But I feel my choices are let it all go, allow her to rule our lives and be miserable and resent H forever. Or let him resent me for what I think is healthy boundaries.
He does not see how much this has affected his entire life, and I was quite blind to it before her being around so long. Mind you, she was barely around most of his life prior to me coming around.
I just need help. How do I help him see this isn't normal? And get him to see him lashing out on my isn't directed at the right person?

[Notwendy]

I think this is a situation for couples counseling and also invidual counseling for your H if he's willing to do it. You may be thinking he's not the problem- his mother is- but the behaviors you see as "not normal" for him are the "normal" he grew up with and so, he may not be able to see them as a problem as well as you can.

There's also the "Karpman triangle" dynamics. If you push against his mother, he may have a tendency to see her as a victim and step in to protect her. Chances are, he's behaving like his father- who role modeled this behavior- and a father is a main role model to a child.

When you say he didn't speak to his mother when it was just the two of you, it's possible that she's invested in the role of grandmother. My BPD mother doesn't show attachment to me but she wants the role of grandmother and so shows interest in that. Seeing that her connection to the other grandchildren involved boundaries- you and your H are another chance for that.

Your H may also have hope of a better relationship with her. We kids, growing up, can get the message that our mother's issues are somehow our fault, that if only we are good enough, we can fix this situation. I also hoped that by doing so, this could be achieved but the limits to a relationship with my mother involve her BPD.

If we learn certain behaviors growing up, we can learn different ones but it's a process, and it can take some time. Saying "no" to my BPD mother is difficult due to her reaction. It may not make sense that a grown adult is fearful of their mother but we weren't always grown adults- we were children and afraid of her reactio. We can rationalize these feelings now but it's a learning process.

[HappyChappy]

... He does not see how much this has affected his entire life, and I was quite blind to it before her being around so long. Mind you, she was barely around most of his life prior to me coming around.
I just need help. How do I help him see this isn't normal? And get him to see him lashing out on my isn't directed at the right person?

Exposure to a lot of gas lighting does destroy trust, so maybe your points are better coming from a trained, impartial therapist ?

We all pick up good and bad traits from our upbringing, so here again, knowing it's considered "best practice" may help ? Couples therapy would also give you an opportunity to make these points in a safe environment, maybe ?