What you said about the children being better behaved when he is away.
I've been left 2 weeks now. Even the dogs are better behaved, never mind the children.
Dd1 is still messy but not as cheeky or sulky. Asking her to help no longer causes a monumental strop.
Dd2 is very tidy. She makes sure her friends all hang their coats up and put their coats away when they visit. Unfortunately she is still very noisy.
The dogs are now both fully house trained and no longer beg guests for food. We had a baby waddling about waving toast all over the place a few days ago, neither dog batted an eyelid.
The house feels so much more peaceful, even when it is filled to the brim with extra children, in fact I am much more tolerent of children noise now.
We all had hot chocolate and marshmallows last night. Dd2 spilt her hot chocolate. No one screamed, no one called. anyone any nasty names. A lovely moment was not ruined over a bit of spilt milk.
Dd2 finally has the pet rats she has begged for for months if not years. I have never seen either child so happy and relaxed.
Don't give up OP. It will change your life in ways you can't even see yet. I found CAB to be a great source of help. They'll know of local organisations who can help you.