This advice is great if you want answers to make you feel better.  And these answers are fine if you do not answer to God!  The era is do what makes you feel good.  These answers are of no moral fortitude.

Pills and a bad husband are not grounds for divorce.  If you want a real life answer on a concrete foundation of truth then here it is.

Dont go back!  Dont get Divorced!  If he is crying and begging you have him nuetralized and in a position where he will most likely negotiate.  Get him help, see his progress over the next year and see him on a date night once a week and allow the kids to continue to see him as much as they like.  if they are alienated from him then gently get them back in front of him when he sobers up.

If there is a medical condition for self medicating such as an injury then this needs to be addressed as well.

Marriage is a commitment/not a choice.  Difference when you choose you can change your mind.  Commitment means for Better or WORSE. 

There is also a chance and I am not saying this is the case but it takes to make a marriage fail.  Is there a slight chance that he is escaping the pain of life withthe pills?  If so you must do some serious self examination.  We are all selfish creatures, and we all take more than we give.  To truly get what you want out of life or anything/anyone else you must give more than you take.  this is the opposite of what we usually do.

There are 3 reasons God allows divorce:
Adultery
Death
When a non-believing spouse chooses to leave we can let them go but, we are not to leave first.

This may not be the advice you seek but,  it is without a doubt the only truth to your answer.

Remember, feelings will lie to you.  Truth even when it feels impossible is truth!