Yes, the drinking is excessive, but I think what Bill is trying to say is that even if he were to stop drinking the other problems that he has would still be there.
The depression would still be there (from what you write I think he IS clinically depressed)
The OW addiction would still be there (those endorphins and the "rush" they produce are some pretty powerful stuff)
The MLC confusion and fog and funk in his head would still be there.
No doubt, the drinking is a problem, but he's using it to run away from a whole host of other problems that are not going to just magically disappear if the alcohol goes.
I think you are right, that the drinking does need to go, but don't think that all his problems will be magically "fixed" if he quits.
I think quite the opposite myself. His other problems (for a while) will seem magnified to him since he's no longer using an ecsape mechanism.
He does need to drop the escape mechanism so that he can face his other problems head on and quit running from them, but he will still have a long road ahead even without the drinking.
I think Bill fears that you are putting ALL the blame on the alcohol and think that if he would just stop drinking then everything else will fall into place and he wants you to be prepared if/when that doesn't happen.
BFM
There is only one person who could ever make you happy, and that person is you. David Burns, Intimate Connections