Has he always been like this? His behaviour sounds irrational and attention seeking. I'm not sure how common self harming is amongst adult men.
He sounds as though he has little regard for you and is very selfish. I would imagine, with a young child, you need all the emotional support you can get, but it seems, from what you say, he is only interested in satisfying his own needs.
Perhaps some kind of counselling would help him. I think if my partner was behaving in this way, where he was harming himself and possibly threatening to go further, I would attempt to have him sectioned.
You have to ask yourself how long can you continue like this and what will be the best course of action for you and your child.