My boyfriend will commit suicide if I leave him

Anna says:
This is the 3rd and last time i am asking this today, The past two times everyone said that he won't do it. He's attempted suicide 11 times in the past 2 years and his parents have confirmed this and said they've walked in on him before during an attempt quite a few times. I would say how he did it and how he failed but i really don't want the memory of all of that stuck in my head for the rest of the day.
I'm stuck in a relationship with this guy who i don't like any more. He's constantly depressed and sometimes suicidal and grabbing the nearest knife but he doesn't do anything because of me. Without me he would of killed himself by now and he's said to me "I'm only staying alive for our future" and "I have you so what's the point in killing myself". I know for a fact he does not mean that as emotional blackmail, He's the sweetest most caring guy i've ever met and if he someone as accidentally hurts me (Example: Turning around not knowing i was behind him and bump into me and i say ouch, he'd want to break down and cry and profusely apologize for hurting me). He also says he's only staying alive for me to make me feel better because i have complained before that he doesn't take/listen to any of my advice but he does mean it nevertheless.
He's the most pessimistic person on Earth, And i'm a realist/optimist so obviously things aren't working out. He thinks the whole world is against him and when he's depressed and vents to me i end up getting depressed, he's made me suicidal once. I want to enjoy life again.
The thing is, If i break up with him, me and him BOTH know he has nothing left to live for, family hates him, his friends don't care, etc etc so i can guarantee he'd go straight downstairs and pick up the knife and slit his throat. It would be too late for the police to get there as he knows where the main artery is so he'd bleed out in two minutes and i obviously can't tell his family because as i said, they hate him and don't care, Same as friends.
I've forced him into counselling now we're just waiting for them to get back to us with a date and time which will be a few months. He flat out refuses to see a doctor or go to a psychiatric hospital. 

This man has severe clinical depression. I am afraid it is indeed frequently fatal. He cannot help it, it is a genuine illness that requires a medical intervention. However, none of this is your fault, and neither are you responsible for his wellbeing. if he didn't attempt suicide over you he'd attempt it for another reason.

It is a very big ask indeed to attempt a relationship with someone with a severe mental illness. I know - my wife has acute Delusional Disorder complicated by OCD. The only reason we are still together is that she is willing to do what I say and faithfully take her medication, so the condition is well-managed and she is currently in remission.

Unfortunately that's actually quite rare - most sufferers will NOT co-operate and obey instructions. That is not your fault. This is your life and you are entitled to live it free of coercion. I know you will feel bad, but if this is not what you want, walk away now. If he takes his own life, he has made that choice, not you.