Someone is bound to be along in a minute who will know exactly what to say.
I think there are much wider issues here than just whether he'll be able to help after the c-section. Is he able to be a loving and supportive partner and father when he's high and/or drunk? From your post it doesn't sound like it, and I'm not surprised.
Also, will you be relying on him financially when the baby is born? If he's not able to go into work through lack of sleep etc etc then that's obviously leaving you in a vulnerable position.
I think it's fairly obvious that he needs help for his addiction (which I know you're aware), but please do remember that your priority is yourself, your unborn child and your older child and that you don't have to put up with bad treatment or extra stress, or have to look after him.
In terms of how you'll do after the c-section? I don't know. I've read that some people can bounce back really quickly, for others it can take a while. It could go either way for you but it's important to have the support in place just in case.
As I said, someone will be along in a minute with some good advice 