bless your ferrety fur, never post anything negative about step children any where other than here. I know it sounds awful but from my experience as a mum before I was a step mum, the thought of another woman having my children with her and another woman being with my ex, and then that woman slating my children and my parenting... would have made me see red.
A lot of people on that thread are applying your situation to theres I'm afriaid which I suppose is natural.
You do not have to 'suck it up' I was in fact playing 'suck it up' bingo as I read that thread and I knew someone would use it. It's bollocks, not to mention a horrible visual phrase that makes me think of sucking vomit off a carpet.
However, what i think you do need to realise is that it is their dad's job to discipline them. You need to sit down with him and convey the facts. Not emotions or opinions. Don't say "your children are naughty/badly behaved" etc. Say "on saturday your DS1 hit DS2 and he swore 3 times using shit/fuck/ whatever. They have spat at DS2 and they have broken my best royal wedding commemorative plate etc etc"
Tell him how it makes you feel and what your concerns are "it makes me feel uncomfotable and edgey and I am concerned that the other children will pick up on it"
"I want you to start disciplining them and use a reward chart (or other method, all 4 children could have the same)"
"if you do then we can continue to spend holiday time together, if you don't then I am sorry but we can't"
The end bit could threaten what ever you feel comfortable with sticking to. Because you have to stick to it. Re-gain control. Don't allow these little hoolums to rule your life.
They're being done no favours, kids need boundaries and disciline.
And forget about blaming their mum by the way... it's a good way to ofset anger towards your DP and the kids but it'll get you no where. I have a big brick shape printed on my own forehead that tells that story.