I hope I'm not too late with this reply, but please don't kill yourself.
I can understand that you feel suicidal and you have been let down by the people who should help, but if you are dead it's the end of any good feelings as well as bad ones.
I don't know how to articulate this, but you say you feel more at peace having made the decision - can you try to keep the peaceful feeling by acknowledging your determination to kill yourself, but putting off the action? (I say this because I have been depressed off and on for over forty years and as long as I have a death plan I can hang on through the worst of times).
I don't know what else to say, but please at least reply and tell me I'm daft - that way I'll know you are still alive.