You are in a really tough spot Hypermom. It's hard to try and watch someone 24/7 and his attempt should be taken very seriously. Like you, I wish he'd been hospitalized for at least 48 hours.

Have you asked him why he wants to die? I'd "force" him to talk about it, not deny it. I can recommend a good book, short and maybe he'd read it too.
Suicide, The Forever Decision..I'm away from home so I can't give you the author.

Please know that you aren't alone with this struggle.