Wait wait wait before you tell him anything.
Firstly- HE needs to move out not you!!!
The children deserve to stay in their home.
It's easier and cheaper for one person to find a new place rather than everyone else move and the one problem person gets to rattle around expensively in the family home.
The extra disruption to the children will not help their copng with it either.
I sugest you tell him that you need space and he needs to move out. If he will not give it to you then you will take that as a green light that he has never got any intention of taking your feelings into consideration and then YOU will move out, with the children. That will of course be far more expensive on the joint funds, and it will also be final, as he's shown ultaimtely that he puts himself first and you'll be DONE.
If he is willing to move out, you will start the process of supporting him through counselling, whatever.
If he refuses and makes you go because he won't then he can fuck off and do it alone and you'll file for divorce.
Don't say ANY of this until you have secured all access to savings, joint accounts etc as it's quite likely he'll immediately take joit funds either to spite you or to prevent you being able to go or to protect himself.
Is the house yours or rented? If yours, another thing to think about is that if you leave, you will have the damndest time being able to sell it for a split, because he could and probably will make that near impossible, dragging it out, refusing viewings, trashing the place. If splitting means a house sale, make sure you are in charge of that by being the person still in the house.