Alright pea,
I tried. I tried as hard as I could possibly try to make it work with your Dad. There are a lot of things that you won't understand for a long time about the spot he's in right now, but it's not a spot where he can be what we need right now. Besides the health implications for you of staying in a life with that much stress, I want to make the kind of decisions I hope you will make some day.
There is one purpose to life...be happy. I don't mean you need to be happy all the time, or you need instant gratification, but overall you should regard your life as a happy one. When you find yourself in a place in your life where you are unhappy far more often than you're not, something has got to change. And that change can be extremely hard, and it may make you temporarily miserable, but it gives you a chance to find a new path that can get you back on track.
It was a very tough call. I wish that I had set up a life for you that had 2 stable parents, but it wasn't an option I had. I promise that you will be loved unconditionally by more people than most. I don't know what your Dad's involvement will be yet, he's not in a place in his life where he can figure that out at the moment.
I made this decision because I thought it was the best chance at giving you a happy and healthy life, which I think is far more valuable than an unhappy traditional family. Don't worry kid, you will be well taken care of regardless of what form your family takes.