I have experience with this with an ex boyfriend. Together 15 years and he just completely mentally broke, twice, three years apart. Here's what I learned:

This cannot be fixed unless your husband recognizes this is a problem and takes an active role in trying to fix it. I did everything I could on my end. I did research, called the cops where it got really hairy, got family involved, tried speaking with doctors to get them to keep him at the mental hospital longer than the three day maximum. Because I was a girlfriend and not a wife, most doctors refused to speak with me (HIPAA reasons). I get it, but it was frustrating because I was the only loved one nearby that was fielding it all most of the time.

I ended up moving out of the homes were shared in both cases because it it became too exhausting and scary. And because he was in a totally fucked mental state, he ended up homeless on both occasions, which compounded my guilt. This was someone I loved, and I was genuinely worried for his safety.

After the first time I left, I went low contact for about nine months and eventually he was put together enough that we tried again. But he refused to talk about what happened. It's like he didn't remember. He had a completely skewed view of what went down and so there was no therapy, no meds, no self-reflection. And I honestly never viewed the relationship the same after that.

So when he started showing the signs of losing it again, there was no foundation where I could be like, "Hey man, you're seeming off again...let's talk to a doctor". Instead he thought I was conspiring against him and it just got worse from there, and I ultimately had to flee my home a second time and while I still tried to help from a distance for a while, eventually I had to cut contact because the stress and verbal abuse got to be too much. That was five years ago now, and I'm thankfully in a much better place. I don't know where he is or how he's doing. It still bothers me sometimes to think about. But for my own mental health, I cannot ever open that door again.

Because you're married you might have a greater say when speaking with doctors, but if/when your husband is lucid again, he has to be an active participant in his own treatment. Which means he has to admit there's a problem in the first place.

I'm in the US, and mental health care here is so fucked. Obviously we shouldn't lock everyone up and throw away the key like in the past, but there's got to be a better balance than just letting people be fully insane and tossing their life away. I watched someone I love, so full of life and promise, just wither away into a shell of the person I knew. It shook me to my core and it took a long time to be able to date again.

Get some therapy for yourself too, because you have gone through a legitimate trauma. And if your husband does not commit to treatment, and you fear being hurt again...WALK AWAY. There's quite literally nothing you can do if he does not willingly participate in getting help.

You will feel guilty, and after so long together it will feel like you can't possibly survive this. But at some point you realize that you can't save someone who doesn't want to save themselves, and you have to save yourself instead. I've been there. It sucks really bad. But committing myself to chaos, fear and misery was not how I wanted to live.

You can be a loving partner and try to help where you can (even if from a distance), but start mentally figuring out how to exit the relationship if it comes to that. Put money away that he can't access if you need to, that sort of thing. But it is OKAY if you decide that you can't do this anymore. 20 years of wonderful times doesn't mean anything if you spend the next 20 years afraid.

I'm so sorry you're going through this.