Dear Changenamer - so, an honest relationship with your daughter isn't your priority 
Because that's what it boils down to.
One day she will find out about all this. She is not stupid. And she may not see your actions the way you do.
I completely understand what you are trying to do. Thinking you are a good actress and can pull this off is not sustainable though. I understand that your priority is your daughter's well-being, and given that, you have worked out this plan and are prepared to sacrifice your own happiness.
But when it comes down to it, the best way for a little girl to be happy and normal, in the long run is for her mother to be happy and free. Whatever you do now, you are teaching your daughter is how a woman's life should be.
I know you don't want people saying things like this, because you feel you have got it all sewn up/under control, and that you are sure you are doing the right thing.
However good an actress you are, you are still allowing your child the experience of living with an alcoholic, who you rightly say you are enabling, and this will not be disguised.