You’re being abused.
Is there a reason for it? Yes - more than likely it’s the SZ. But just because there’s an underlying reason for it doesn’t mean it’s not abuse and it doesn’t mean you’re not a victim of it. From what you’ve described, you’re more or less a prisoner - you can’t do much without being interrogated, you’re being pulled away from your family and you’re on the receiving end of what I assume to be some very nasty and untrue remarks.
For your own sake, I think you need to cut this off for the time being; as in, no longer live together. You need to do that for you and for your family. I think the environment is too toxic to really do much else. I’m not suggesting break up permanently - he needs to be on medication, in therapy and in contact with the right people before it’s okay for you to resume a relationship with him. This isn’t something that can really be negotiated and you need to keep in mind that your own mental health isn’t impervious.
They use the term ‘co-dependency’ to refer to couples who are stuck in destructive cycles but can’t pull away - this is what you will likely become if you don’t put a bit of distance between you so you can regain your freedom and help him without being in the thick of it until things show improvement.
I was in your shoes and that’s what I did - not easy, I loved him and he was my first boyfriend so it felt like the end of the world…but it was the right thing.