Partner doesn't like our newborn

Partner keeps making comments and saying he doesn't like our newborn. He was absolutely perfect with our first so this is completely new. I'm really not sure what to do because he won't go and get help which I've been trying to get him to do for the past 6 months. He won't try antidepressants, and every psychologist appointment I make for him he doesn't show up to.

He wanted to put my oldest to bed because he didn't want to look after the baby so when he came into the room I said "are we swapping?" (Meaning who we are looking after) and he said "either swap, or kill it, doesn't bother me.". Even though I know he wasn't serious, It's comments like this that I can't handle. He is talking about one of our children.

He is the perfect dad to our first so I'm so conflicted with what to do or what I can do. Has anyone been in a similar situation? Any advice?

I don't want to leave but it feels wrong being with someone who speaks about one of my kids like that.