For me personally I wasn't actively planning self harm but was just tired of struggling. The way I put it was "If there was a button to press for it all to end then I'd press it". I do think these thoughts can sometimes spiral towards actively planning in some people though, I don't want to worry you unnecessarily but nor do I want to give you false reassurance.

It must be very hard for you to cope with what he is saying, but is the illness which is making him think and say these things by the sound of it, it is unlikely to be something he intends to upset you with.

You do not have responsibility to make him well, and you may have to accept his reluctance to engage with treatment, but if there is a crisis team and you are worried about him then maybe you can get in touch and consult them.

In the meantime take good care of yourself.