As your SKIDs are adults and don't live with you, I think it's good that you put your cards on the table.  I don't normally recommend sharing with partners, the fact that one is disengaging, but I think in your case it's a good thing to do.  One cannot collude forever with members of one's partner's family treating you  poorly.   

I am now disengaged both from my DH's two adult daughters, and in addition both DH and I are estranged from his mother and step father for over a year, because of the way they treated both of us, but principally me.  Eventually you have to advocate for yourself, and say "up with this I will not put!" 

Good for you. Don't buy into your DH's "poor me, you'd be better off if I left" crap.  He can have his pity party on his own - I'm sure he contributed in some way to the issue you are having.

He'll get over it.

It seems to me the time to fix things with his girls was years ago, when they first started displaying poor behavior in their youth, followed by the first time they treated you poorly.  

Now the only sane thing to do is disengage.

I would have responded that it was so awesome he was fixing things. Let me know when they are fixed and give me some evidence of their appropriate behavior.

They see you in the way of their inheritance. Even though you make much more than their mom, it doesn't matter. Their dad should be spending all time and money on them and their children. All the other complaints are hogwash. This is about $.

Reading your prior post.. It seems that both of your adult children live with you and your DH.  I'm curious how he took you "disengaging" from his children (also adults) that don't live with you while he is expected to live with your adult children in the same home?

That is going to cause resentment with him in the future I'm guessing.

"He even asked if my life would be better if he left"   Which was a threat in disguise.  My DH used to do this all of the time until I finally called him on it and told him I would buy him out if he wanted to really leave. 

Sometimes it seems that when our DH's get buddy-buddy with the skids they come to the conclusion that we are not as intelligent as they are.  This could be due to the way they view us.  After all, who else with any intelligence would be bending over backwards for approval and acceptance from people that treat them like dog doo?  So when a disguised threat of "He even asked if my life would be better if he left" comes at us we'll do anything to protect our unrealistic dream of the perfect blended family.  Even if it means selling ourselves short.  My DH used this tactic to control and manipulate me for years.

Please take my advice.  The next time he puts forth the 'suggestion' to leave, reply, "If that's what you really want", and watch him stumble over himself to backtrack.  Believe me the look on your DH's face, when he realizes you are smarter than he had assumed, is absolutely priceless!

You may think they are perfect, but I can see this creating tension.  Is there a plan for them to move out?

Welcome to step misery world. We get to the bottom of the bucket and then we pullout altogether, like you.  You have to protect your own emotional health away from these "girls" which are anything but, I imagine.  As nasty as they behave is is easy to lose sight of the real culprit, dadddeeeee. 

So, whatever he says, or threatens, you do what you have to do to not deal with the mess he created. Most of the time it is so messed up they seriously cannot fix it, even if they wanted (wimp daddees). We, have little choice in these cases, but to disengage.

Happy you are taking steps in the right direction; do not turn back.