Hedgehog, what's happening in your family is not sustainable. That's the crux of it. Regardless of who holds the 'moral high ground', your behaviour as a couple is going to be affecting your children and that's not on.
What other help can you access? If I were in your situation, I would go to my first port of call that would be my GP and I'd explain the circumstances. It's completely unacceptable that only you/your husband can care for your daughter's cannula. You're not trained medical professionals so what makes you think that a nurse couldn't be called in to assist? If you had some help there, maybe it would free you BOTH up to do things individually and as a couple/family.
Something is really nagging at me, Hedgehog and I'm sorry that it's going to sound hard but, you sound an intelligent woman, why wouldn't you keep plugging away at the various agencies on a 'rinse and repeat' basis until you get some help?
I also wonder if, keeping the care of your children 'exclusive' to you and your husband, that you retain control of him and his movements to an even greater degree? To allow others in would possibly relax the 'hold' that you want or feel compelled to keep?
The thing is, if you get to the point where either of you cannot stand each other, you will each be doing this alone anyway... that is the future unless you can operate effectively as a couple or, if not that, as a unit of parents.
The money to family is water under the bridge now, no? You have your husband's wages and bank card so you know that's not going to happen again. Don't let previous stuff that's unrepeatable, clutter up your thoughts because you both need to be clear-thinking and work out a plan to access the help that you need for your family. Harping back to it all the time (if either of you do that) is really counter-productive.
MN is a great place for support but if it become a crutch, like the TV, then it's not a good thing. You both need to talk to each other and find a way through that you can agree on, for your children's sake.
Have you and your husband had a sober talk yet? When are you going to do that?