You would be better placed using resources to have one to one counselling for you first.
It’s really important that you develop an understanding of the deficit in your boundaries to have let this get to this state.
You need to build yourself up b clearly - otherwise you will go into couples counselling with dangerous and risky levels of pity and over responsibility for him.
Focus on you and how you with support your DCs through this.
You will need every once of your finite emotional energy over the coming year - preserve it and direct it to you and your DCs.
Don’t let him drain you of this precious resource, don’t let him take it away from your DC who need it more than him.
He has caused the heartache that your DC will endure.
He has had his fill of your support and generously and he has exploited it and abused you and hurt your DCs.
This is his own emotional journey now - and it will be a better, more authentic, sustainable one (which in turn benefits your DCs) if he works through it all himself and has his own intrinsic motivation rather than you involved enabling and facilitating some false narrative. That’s what has been happening to date and it is dysfunctional.
You really need to work hard to understand why you feel the need to continue to support him through this - because it will be at the expense of your DCs emotional recovery.
He will manipulate and exploit. He will push boundaries. Look up the script. Sulk, beg, plead, blaming, shaming, threatening (suicide) - you have all this manipulative and punishing nonsense to come and you can allow yourself and your DCs to be whipped up in his psycho drama - and be emotionally harmed or you can emotionally detach and withdraw and resist any urges to help him and protect your DC from the fall out.
What was your childhood like? I see traits of over-responsibility and co-dependency which have laid you right open to this exploitation.