You sound sooooo ready to take this step! And I hope you have a good lawyer who will hold your hand through it. It was incredibly helpful to me to have a lawyer who knew all the ins and outs and could advise me when we got to a point where I needed to make a hard choice.
I won't lie to you -- divorce is emotionally draining, even when you know that is what you want to do. So make sure you keep reminding yourself of WHY you are doing this. Reread your old posts, journals, e-mails, whatever, so you never let yourself forget that you have good reason for getting a divorce even if it feels hard at times.
Two of my kids were about your girls' age when I divorced AXH. I can't begin to tell you how much happier and healthier they are now. It's been hard for them, too -- I don't care how dysfunctional your parent is, it's still difficult when they abandon you. But you sound like you will do whatever it takes to get them and yourself through this. Good for you!