Agree with Gimlet.

He knows that he is in the wrong for not standing up for you. He wants you to be mad, so that he can be mad at YOU, instead of himself, for allowing this disrespect in the first place.

He may have encouraged you to disengage, but he didn't mean it, or didn't think you would actually do it.

He really is a jerk.

^^^This ^^^

He’s mad at you because that’s easier than being mad at anybody else, including himself. He knows full well that the situation is wrong in so many ways but if YOU would just smile and accept it and take their beatings, it would be so much easier on HIM.  

Uhm, no. I wouldn’t waste one second dealing with his little mantrum. 

Next time tell him to do that gaslighting bullsh!t on someone else because you don't care about what he does with his daughter and grand kid. It has nothing to do with you, so try it on someone that cares because you damn sure don't.

Turn that crap back on him and make him own it. He has some nerve!

Bethany, your H has problems, both as an individual and as part of the dysfunctional dynamic that exists with his people. He's screwed up, and you know this, so you need to exert self control and not let him provoke you.

You've chosen the path that works best for you - disengagement. You've changed, but he hasn't and is still caught up in the crazy. His life was much easier when you were participating in the dysfunction, so he's likely unhappy that he has to handle the emotional labor himself. He had dinner with the Ahole family, they probably all talked carp about you, and he came home primed with resentment. He was looking for a reason to fling toxic poo at you. 

You and I both were married for quite a few years before disengaging, so our damaged spouses got used to us going along with the crazy. For them, change is both difficult and unwelcome, and takes longer. When I first disengaged, my H would do the same thing. He'd meet up with the in-laws, they'd complain about me, he'd come home, and their poisonous words would come out of his mouth. It took a good while of me consistently standing firm, refusing to get sucked back in, and not taking the bait before my DH accepted the new norm. And because I was steadfast, busied myself with positive endeavors, and kept a drama free home, my DH came to realize that in-laws = upheaval, pressure, and negativity while I = peace, acceptance, support, and calm.

You're in the early phase of disengagement where the players haven't accepted your stance and are testing your boundaries for weak spots. Keep a few bland statements handy ( That doesn't work for me., This is best for all of us., etc) and a few home truths (They want you, not me., Why do you want me to go where I'm mistreated., etc), but don't let your H drag you into any arguments. You'll get him retrained, it just takes time and commitment to remaining disengaged.

his grandson left on YOUR IPAD? My guess is he didn't.

Many of these men always point the finger at everyone but themselves.

Disengagement, when you KNOW THEY ARE TALKING ABOUT YOU when you're not around is tough. I don't even want DH around his toxic kids. 

As another poster wrote, when her DH got with his kids, she knew they were resentful and discussing her and she heard their words come out of his mouth.  It's the truth. I cannot tell you the things DH has said to me that sound PRECISELY LIKE SOMETHING this horrible SD would say. When that happens, I call him on it, and call him by HER NAME.  Once he told me, "What goes on in the family business is NONE OF YOUR BUSINESS." That sounds JUST LIKE SD. My response was, "ANYTHING YOU DO WHILE I'M WEARING THIS RING, SIGNIFYING I AM MARRIED TO YOU IS MY BUSINESS. AND I MEAN ANYTHING."

I'm in agreement with several others here. This is not a healthy relationship. Just look at many of the posts people are asking for help with. The Adult Step section GETS THE MOST TRAFFIC FOR A REASON! Even when the grandson is grown, you'll be forced to deal with his antics, unless you get out. DH will always come to their defense, and you'll always be chastised for speaking up, or making observations. People do not get defensive when they have nothing to defend.

That Sparents tolerate their own spouses who are driving this kind of toxicity never ceases to amaze me.

It is mind boggling.

There is nothing redeeming about assholes that create this kind of multigenerational genetic behavioral refuse.  DH created his crotch rot of a daughter who created a rotten crotch dropping of her own.

Some gene pools have no business existing at all and those who initiate them should not be tolerated to ruin yet another partner's life.

Move on. Live your life free of this shallow and polluted multigenerational genetic cesspool of crotch rot.  Leave your SO to simmer in the stench he has created.  That he blames you for his GK's toxic crap that was left open on YOUR tablet tells the complete story about all of that shit filled family.

Live well.  Take care of you.