The only part of your comment that makes sense is where you agree that this is a crisis and he needs to not be with her unsupervised. I'm not sure why you're ranting at me.
Nobody can make him do anything at all
OP cannot make him raise her, cannot make him develop strategies or anything else.
Where did I say that OP or anyone should make him do any of these things?
If OP tries to force the man who has just said he wants to throw his daughter off a bridge to parent, he will probably just leave - and that's best case scenario.
I don't see anywhere in my post encouraging anyone to "force the man" to do anything, do you? Why are you putting words in my mouth?
and nobody can make him change his feelings.
I disagree. Yes a professional can help him work through his feelings. This could be some sort of situational depression or whatever it is but he need to see someone. He needs serious therapy for these thoughts of harming his child!
No I don't agree that OP should be the one to find the solution for him. Yes, OP can suggest these solutions to him afterall they're a couple. He doesn't need "convincing" as if he's a victim here! They need a social services needs assessment for care and respite, yes. He needs to speak to someone ASAP and keep away from her in the meantime.
We know that he would have to want to do these things for them to work but OP needs to protect her child. I'm not sure where you've read otherwise or why you seem to think that shouldn't be a priority.