Agree with PP s about emotional blackmail/manipulation and a out migraine!
I had these on and off and there is no way in the world I could have opened my eyes or looked at a screen. He may well be a migraine sufferer but he also finds it convenient to announce one whenever you're around.
Bottom line: your husband has left you. He has left the relationship; he has given up caring for the children while you're there; he has abdicated from all financial responsibility.
He has left you. There's just a needy fake invalid where he used to be.
Don't ask his permission to get the help you need in the house and with the children; just organise it. I don't doubt he's terrified of someone else being in the house on a regular basis seeing what he's done to you. Tough.
Meanwhile, you are completely entitled to stop enabling him. You don't need to announce it, just do it. Stop discussing or listening to his health concerns, just "Okay," when he tells you he's off to bed again. Stop fussing him to get help. Stop asking him to pull his weight. Stop expecting anything - he's not there, remember?
Likewise, stop servicing him. Laundry, meals, shopping, messages etc. Don't lift a finger for him. If he wants a glass of water, he can fetch it himself. Deprive him of the oxygen of your attention and concern. Remove his audience.
Plan your life and activities as if he didn't exist.
How boring can you make it for him? Why not take the router with you whenever you leave the house? If you're paying his phone contract, stop.
If you are paying into joint accounts he can spend from, re-organise finances so he can't just dip in. The gambling thing demands this anyway.
If he cannot or will not help himself, it's futile for you to expend time and energy trying.
Next time he tries emotional blackmail over self-harm, calmly tell him his life and body are his own and he must take 100% responsibility for them and what he does with them.
He wants you all gone, I think, and is waiting you out while he wears you out. He may also think that by taking to his bed, he is making himself divorce-proof. I suggest that he is not. Yes, it sounds bad - she divorced him while he was debilitated?! - but you have enough evidence of unreasonable behaviour to start proceedings now if you want to.
How is this impacting the children?