Ok stop drinking immediately, that's the first step as you said.
Second step is to really understand parenting. If she feels you should be doing things with your son, and that you haven't bonded with her daughters, then you probably are really missing the mark with your kids and step-kids. Read all the books you can find on this topic and become a better parent. That alone will increase her attraction to you!
Then read the DB book, have you ordered it yet??
As for her declaration to when this split up might occur...you will have to learn patience and detachment here. That is the noose around the neck of all LBS's here (left behind spouses). It is difficult, but you have no choice. You must just accept what comes, but at the same time, divorce-bust your butt off in the hope that there will be another chance for you and her.
But I can say as a woman, if my man wasn't being a good parent, had a "negative, critical and controlling" attitude, I'd want out, too. So first and foremost, learn how to stop that right away and become a good parent! THEN after you've learned these things, you will have a chance at reconciling with her. Without those things, you won't.
