Different people drink for different reasons. Many times, drink is used to calm nerves or other emotional issues. That doesn't mean that the person has serious mental problems; only that they never found out the correct way to deal with issues in a healthy manner.
Regarding the neediness, I too was married to a man who made me feel like the sun rose and set in my eyes. That gets old really fast. It got to the point where I couldn't even go into another room to read a book without him coming in several times asking if I was mad at him. Eventually, I was mad because he wouldn't leave me alone to read! While that might not bother some people, it nearly drove me mad. Your man sounds very clingy and insecure.
Only you can decide what you are willing to live with. Just because he stayed with someone who literally drank herself to death doesn't mean you have to, and it doesn't mean that if you don't stay, you don't care about him. You cannot save him no matter how much you may love him.
