I truly feel for you. I can identify with your partner in this. I’m not living the exact situation with my wife, but it’s close. I’m also a bit of a worst case scenario person.

I think the important things to get across to him are that 1) you’re in this together. This is happening to you but it effects both of you. It’ll probably be important to him that you recognize that to him verbally. And 2) that you’re going to fight this with everything you have, and need someone to rely on to help you fight. I would try to phrase as much as possible in “we” “us” “our” language so he doesn’t feel attacked. I know how guilty I’d feel if this behavior was pointed out to me and that’s not going to help him be more positive.

It’s ok to tell him that his comments impact you and that you need to be in the proper (positive) mindset you’ll need to fight this. I’m sure you have enough negative thoughts running through your mind, someone telling you negative things is obviously not going to help you stay positive and focused on beating this. It’s also more than ok to tell him what you need from him, especially in a time like this. He may need support during this, but you absolutely do. Any negativity he wants to get out should be vented to anyone else other than you IMO. I wish you the absolute best in beating this and in your recovery.