Why does bringing the tree in the house have to include him? Can't you and your two teens handle the job without him? He needn't spoil your tree-trimming festivities.
You say you want to leave him and I can certainly understand that. What steps are you taking to position yourself to be able to do that? I found it more productive to focus on actions I could take to improve my circumstances than on what my ex alcoholic boyfriend was doing or not doing. Focusing on him just kept me stuck in a miserable situation.
Why not whip up a batch of hot chocolate for you and the kids and continue your plans without him?