OP, you sound like a really great woman, who has been doing it all for a long time.
I don't believe you can turn your MH issues and depression on and off the way he does.
I think he has gotten into a habit of being a grumpy man and you have indulged him by being as supportive as possible.
This has slowly escalated and morphed into him being a really spoilt, cranky, abusive fxxk....in which the whole family is his emotional punching bag.
How he has treated your children is truly unforgivable.
Combined with his behaviour over the past two years, rest assured that despite your assurances to her, she will NEVER forget this time.
He is not a good man.
He is a very selfish man.
I think he needs to leave the house.
I would be telling him today that you would like him to leave.
That his abuse of his children has gone too far and that you no longer want him in the family home.
This is when you need to be very strong.
Do NOT accept pleas or promises.
Its too late.
He needs to leave the home.
He needs a very firm dose of reality.
Kindly meant, but you have allowed him to think he can get away with abusing your two utterly defenseless children.
I would shine a huge light NOW on him and tell him you want him OUT of the home.
This IMO is your best hope of him getting a grip on himself and dealing with his issues.
Anything else, is you facilitating an abuser in your home.
I genuinely believe you don't want to do this.
It's very hard on you.
But he needs to finally realise his behaviour is NO longer acceptable and it is in the families best interests that he is out of the home...
Let Mr. Happy explain that to his colleagues....fxxker