OP, I'm so sorry you're dealing with this. I too have experienced a husband with psychosis and longterm MH issues when we had very young children.
Like others are saying above, he sounds pretty ill. It's possible that it's been brewing for a long time and is a major contributor to the breakdown of your relationship. I wouldn't call time on your marriage yet, unless you absolutely can't stand the uncertainty.
Is he still working? If so, that suggests that he does have some capacity to think straight and to cope with day to day life. If that's the case, I'd have a very basic talk with him, telling him you'd like more information about his treatment and his living arrangements. If he's gone beyond being able to work, then that sort of talk might not be appropriate.
As a minimum you could ask if he'd reconsider you being able to talk to his care providers.
I think it's OK to let him know (calmly) that this is hard for you, but that - if it's true - you're prepared to give it time, to see if his recovery means that the relationship could be worked on. You could point out that he could make things easier for you, by being more open. Without pushing it, as he may not be able to take much on board.
It sounds like you'd benefit from individual counselling as an outlet for your feelings and a way of processing what's happening to you. ask your GP for a referral, try your women's centre, or look at private if you can afford it. Charities like MIND have resources/groups for spouses too. Take advantage of any help that anyone offers - try to stay healthy and conserve your energy as much as you can. As his wife, you're entitled to a carer's assessment. Even if they can't offer you anything useful, have the assessment so that any unmet needs are recorded.
You won't get anywhere with relationship counselling until your husband is a bit better. He doesn't need to be 100%, but definitely better than he is at the moment before he'll be able to engage properly.
Maintain his visits to the children if you can, if he seems well enough. Try to just focus on making the visits go well - see it as a temporary holding situation, maintaining his relationship with the children, until he's able to do it himself.
I truly know how unfair it feels in this situation. Look after yourself and the children - better days will come, one way or another.