As someone who is on her second round with MLC'r/alcohol abuse, I guess you already know that he wasn't through it when he came back 3 years ago. Did either of you try counseling or any sort of DB'ng after he returned, or was everything just status quo. I know in my sitch, my h had to spend 18 months in Iraq, and that sort of put his MLC on hold. Nothing resolved when he returned.
Hold on Tip, and don't believe for a minute that you have nothing to live for. You have everything to live for. It's HIS problem. As trite as this may sound, things will work out. Trust in God and leave it on his doorstep. Come here anytime and often to ask for help or just to rant.
Again, I'm sorry you are having to go through this a 2nd time. No one should ever have to go through it a first time.