what do I do?

My best friend who has had two miscarriages and is having her first successful pregnancy, called me last night asking me to come over so she can have someone to talk to. So I asked my husband and he told me to go. Bad choice on my part for going I guess. He threw a huge hissy fit and really made me feel like crap for being there for my best friend. Fast forward a couple hours and I head home for him to try killing himself while I'm on my way home. My youngest was in her crib sleeping when this happened. I walk in the door and he's laying on the couch crying. I sit with him for a bit to see if he'll talk to me, nothing. So I go get ready for bed and he tells me he's going for a drive. I tell him to be safe and he gives me a whatever. So I grab my pillow and a spare blanket and go lay on the floor in my girls' room. He comes and knocks on the door wanting to talk. Apparently he's been suicidal for the last couple years and now that there's the threat of me leaving is trying to act on it. My mom calls bullshit on him and I do too. I just... I need to leave. This relationship is becoming toxic and I'm not happy. But I'm afraid if I leave, he'll kill him self. He's accusing me of cheating on him with a guy I used to work with. I don't feel like my girls and I are safe anymore. I asked him to get help and he hasn't yet. He tried to hang himself last night for me to find when I got home. What do I do? Is it selfish of me to still leave? It's making me physically sick with all this added stress from him doing this.