This is excellent!
These excerpts really stood out for me and disengaging (at least 75% in my case) REALLY WORKS!

...In addition, our "criticism" of his kids is seen as a criticism of him...
Yes, DP does this so I have stopped talking about the SDs "issues" at all with him. If something is left out I simply tell him, "Please pick up XX's pens from the floor." And if he doesn't, pens are disposed of.
I cannot say, "Your girls need to learn how to pick up after themselves." He would reply, "Are you saying I don't teach them how? That I don't understand that?"

...What all this means is this: You must stop parenting your SKs. You must stop telling them what is expected of them. You must stop disciplining them. You must turn over all responsibility for them to your DH. You must allow DH to make whatever mistakes he makes.
And every time they ask you for something, or ask permission for something, you say "Go ask your dad." Your SKs may end up missing out on some terrific things because of your Disengaging, but it was a choice they made when they decided to make your life miserable. Never give them the opportunity to treat you disrespectfully....
This weekend SD9 asked me if her friend could stay the night this weekend. My response, "Ask your dad." SD11 asked if she could have a particular expenive soda, "Ask your dad to buy it." Can SD11 buy a new shirt? "Ask your dad."

...You must choose your battles, and to disengage, your battles should be about those things that DIRECTLY affect you. For example, you have a right to keep your home with the degree of neatness and cleanliness that you desire (just leave the SKs rooms alone and concentrate on the communal areas)...
I have complete control over house cleanliness except for SDs bathroom (unless guests are coming then I get DP to clean it stat) and their bedrooms. This was understood before we moved into the new house. Things don't get put away they disappear. Dishes stacking up because SDs use 10 water glasses in 2 days and DP cannot seem to teach them to even load them into the dishwasher? DP does them.

...The aim is NOT to straighten out your SKs deficiencies, it's to get your DH involved with his children, in whatever way he chooses, and to lessen your work load. If the kids are going to be unappreciative, let them be unappreciative of their dad...
YES. DP was very withdrawn in partenting. He pretty much let them do what they wanted until the got totally out of control, then he'd lose his cool in a big way. He's learning to see issues before it goes crazy. He's just beginning to see issues (although still avoiding dealing with them). I've been working on disengaging (a process) for almost a year so it's still new, but I'm much more relaxed, SDs are happy and DP is more stressed (although happy, he's learning parenting is HARD).

I wish I could send this to my co-worker, but she might take it wrong.
She has two kids, marrying a nice guy (who is strict like me she says!) in 10 days.
They haven't lived together before and he doesn't have kids.

However, she's concerned about how they will all get along and talked with me a bit about it. Told her their relationship will change and that she cannot let him discipline. They need to talk about boundaries and kids and rules and expecations. Some of which they have done. What she didn't get was that him moving in will change how the kids interact with him directly - expect rebellion. (But they get along really well...hm, but I see how that could change...).

So maybe I can be a bit of a level perspective for a BM (she's a good one but also has a completely whacko ex that adds another level to her situtation) and her near to be DH.

Sally, just wow chick. I am reading this and it is hitting every single note of how I feel. And I am showing it to my husband who on Sunday said "I feel like you are rejecting Chucky and in turn me by doing what you are doing". He said this when I walked away from them while his child was being very badly behaved.

My words to H were "I have told you I am tired. I am tired of being the only parent in our house to a child who has no respect for me and does not like me. I am tired of the bad moods and anger. It hurts me. You need to parent your child as you see fit, the same as I parent the girls as I see fit."

He was unhappy with me because maybe I have not made it crystal clear enough despite what I know I have said. My H knows I married him with the understanding I would no longer participate in Chucky's life.

Thank you so much Sal! I think my H needs this to help him understand he is the reason the "blending" didn't work as well as Jabba & MIL's influence.