Lies, lies, lies. But assuming it's not (but it IS);
he wasn't going to take the place the council have offered him as it's like a prison cell". He can't have visitors there and has to sign in and out every day.
That's his problem
He also said he wants to end his life,
That's a lie, but if true, that's his problem.
It's ds birthday on sat, and he said he'd taken £200 out of his bank to get him a present, but the money must have fallen out of his pocket as he can't find it
That's a lie, but if true, that's his problem (that £200 was/is probably for a hotel room or the council accommodation).
he says he has no one to talk to, but in the next breath says that he doesn't want friends, and he doesn't want people knowing his business.
That's his problem.
he's going to quit his job and just sleep on the streets
That's a lie, but if true, that's his problem
He is so bloody draining, when will he just move on and pull himself together.
When his 'antics' stop working on you.
I'm scared that he'll kill himself, and dsd and ds will blame me for it
See, his antics are still working on you.
As far as suicide, I honestly believe he won't do that. But here's the thing, you need to be reinforcing to the children that everything he does, every word he utters is his own choice and his own decision. That others don't make us do anything. We all have free will and the ability to do 'something else', anything else, even if that thing is not our first choice in life. It's one of life's most important lessons (if not THE most important).
You have free will, too. And you're starting to exercise it. You've made changes and choices you never thought you'd be able to make. He can and will do the same once he's forced to it.
Get that car back. Tell him he's no longer allowed in your house. It's the last things he has to hold over your head. Once he realizes that his 'poor me' is no longer working, he'll 'move on' and sort himself. He'll probably make it unpleasant for you (cue a fake suicide call or two) but he will sort himself.