I had many nights crying and holding my babies (who are 2.5 years apart) while my addicted ex either didn't come home, or he raged downstairs while we lay upstairs trying to sleep and ignore him. I waited until my kids were 6 and 4 to file for divorce, and we lived together for almost a year while the divorce was finalized. It was awful. My kids mourn the loss of living with their dad, and having a broken family, and they miss living in the "normal" house we lived in then but they are realizing now why I had to leave, they see how their dad makes promises and doesn't keep them, how he gets mad at them so easily, etc.
I didn't mourn what we had, because we didn't ever have it. But I mourned the loss of the dream, of what we were SUPPOSED to have, the happy life we COULD have had together, but didn't. We had everything in the world you could want, a nice house with a huge yard and a pool, two beautiful kids, he had a good job... on paper, it probably looked good. But in reality, it was a living hell for much of it.
I'm so sorry. Do you go to al-anon? That helped me so much with handling the end of my marriage and the ensuing grief.