Your reply to PP suggesting you simply ditch the holiday & leave DH to manage his own children & mother was sad OP. You said you can't think of a friend who would be free to go with you - so what? I would have thought a woman with a f-t job who is also doing the majority of childcare, housework & mental load would be delighted to have a week solo to do exactly as she pleases ...
Have a think about that freedom.
Because your DH's unilateral stunt is outfuckingrageous.
He can't upset his mother - but you don't matter?
Was he with you on Saturday when she spent 2 hours being a bitch to you? He allowed this to happen without pulling her up for insulting his DW?
This is larger than some disrespect over a holiday.
You seem totally blase about the unequal domestic burden.
He seems utterly blase they he gets to call the shots, & expects you to suck it up.
By all means tell him to fuck off.
But not before you have mentally excised yourself from this holiday, & booked YOURSELF something else. Somewhere you can totally relax & recharge.
Then give DH both barrels.
Tell him he is a disrespectful arse who expects you to shoulder the bulk of all domestic responsibilities & is now imposing his mother on you.
Tell him he has broken the camel's back, & you are not accepting his imposition. He & his mother will be in charge of the kids on the family holiday, because you are not going.
If you can't do that because you fear his reaction, or he won't 'allow' it' then you have a serious problem, & PP will support you with that.
Next: holiday or no holiday, unless she falls off a cliff you are still going to have to deal with his mother.
I'm going to be blunt now, so please brace yourself as this IS, I promise you, kindly meant.
You spent 2 hours on Saturday being insulted by the woman.
She insults you BECAUSE YOU LET HER.
This is not a criticism, please don't feel bad about it. I understand how the dynamics of power play build up, & the less powerful person becomes effectively silenced. The barbed remarks that are aimed at you but subtle enough that nobody else picks up on them. The DARVO tactics to prevent you from naming the behaviour. All the plausibly deniable little digs that get twisted back to make YOU the unreasonable-seeming one if you object.
So you end up not objecting, & seething in uncomfortable silence.
My advice is you blow her shit out of the water.
Next time she gets pissed & arsey with you - NAME THE BEHAVIOUR.
It is such a powerful tool, but we so rarely use it!
"Sheila, you're doing that thing you do when you're onto your 3 drink again - making rude comments so please watch your manners."
"Sheila, you're being unpleasant again & I'm so bored of it."
"Sheila, if you can't keep a civil tongue in your head perhaps it's time for you to go home."
"Sheila - why don't you take your unpleasant remarks & shove them up your arse, because I'm done giving you an audience."
Then you just walk out. Calmly, coolly, telling DH that you'll get a cab home & you'll see him when he gets back.
You need to change your mindset.
There is no law that says you have to even be in your MiL's company, let alone endure her insults.
Naming the behaviour is your friend. It takes a bit of guts first time (you might want to practice in secret so you get used to the feeling of those words coming out of your mouth) but it is instantly effective in stopping you from being seen as the doormat MiL can badmouth at will.
And if DH has the temerity to be displeased at you finally standing up to his mother, he can stick his displeasure up his arse as well.
Stop internalising the rage you reference in your update above. Use it, channel it, & unleash it in a controlled manner.
I think you have taken quite enough stick from this peremptory man & his awful mother. Reckon it's high time you took control, & explained very clearly that you are no longer tolerating their disrespect.