You leave: he damages himself
You stay: he damages you, he damages your children, he damages himself
He damages you, by forcing you into the role of parent to him. You're not his parent, you're his partner.
He damages your children, by taking food out of their mouths, and destroying/preventing/ruining their holidays - which are supposed to be some of the happiest times of their entire lives, and the experiences they'll look back on when they're older.
He damages himself, because he suffers even more guilt that he's doing all of the above. He's not just sorry about his own life, he feels bad for all of you. Yet not enough to stop doing it.
How much money does he have to flush down the toilet before it becomes too much? Like, literally flush down the toilet. Would you take thousands out of a cash machine, and then go chuck it in the river? This is what he's done. Thousands of pounds. In the river. Of your money, and money for your children.
You've been told to leave. Anyone else would tell you exactly the same. Pity your children for not taking the advice.