Hi Aranel,
Welcome to the forums and thanks for being here.
I'm really glad you've decided to post and I'm really sorry that you're in this situation. It sounds like you're between a rock and a hard place in doing what's best for him (keeping him safe) vs dealing with his wants (being out of hospital).
I genuinely feel that you've done the right thing in getting him to the ED and keeping him safe, regardless of how he feels about it.
Even though what he is saying must be awful to hear, I'm guessing that he's saying it because he wants and needs someone to blame right now. I say this because so many things are out of his control; he's in hospital, he's obviously battling with the idea or thoughts of suicide and feeling a bit isolated from the rest of the world. I'm sure that if your partner could see things the way you see it he'd agree with you but he's just not in the right headspace at the moment.
You said in your post your partner commented 'being in here just makes me want to kill himself' - then he's in the right place. It's the hospital's duty to keep him safe. He was hurting himself before he came into hospital, so in a sense even if he is deteriorating in there and feeling worse, he is still safe - which is the biggest priority.
I really encourage you to have a chat with the GP or Psychiatrist about this. Latch onto your other support; friends/family. They can help rally with you and give you the support that you need. Maybe this means giving him some space until he feels safe enough to come home, or maybe this means setting some boundaries or having things to say back when he says those comments, or even just having someone else in the room with you for moral support.
