Sweetheart, you need help. You both do. To know that your DP was really, seriously, thinking about killing himself only a few short days ago must break your heart. I'm so sorry that you are going through this but you HAVE to take control.
I would advise that you contact HIS GP. Yes, behind his back if needs be. You need to speak to her and voice your concerns, she most likely won't discuss the conversations they have had (rightly so) but you need to tell her how is with YOU.
Between you, perhaps you can monitor him more closely. Maybe she can tell you what you should be looking for although I should imagine you know 
He needs specialist help, that you can't give him, however much you want to. He would be better in hospital, for his and your own safety.
I'm not saying he is going to hurt you, or anyone else, but so that he can have the treatment he needs on taps.
Waiting is often what causes the damage.
I waited and waited and waited before I asked for help. It was very nearly too late.
Please, please, do what you can to get him seen today. As I said, if you can't get him into the GP, then &E is where you need to be. They will and can help you both. They do care and they will understand.
You haven't failed, you know? You've not let him down. I promise you. But you are exhausted. And you're emotionally attatched and you need to let someone, anyone help.
Be brave and take that first step. xx