" I knew he had a problem when I married him, just not that it would get worse or continue, which is my mistake. We have two little girls and are able to contain the worst of the fighting to keep it away from them."
Welcome, take some time to read the stickeys at the top of this forum and cynical one's blogs.
Unfortunately, whether you realize it or not, your girls hear and see everything, although they internalize their fears. Children will carry their childhood into adulthood. Google "Children of Drug/Alcohol Addicts" might help you to better understand what the real effect this enviornment is and will have on them. I was raised in a home where addiction was present, I still bear the scars today.
Read around this and the Family & Friends Forum, addiction is addiction, whether it be alcohol or sustance abuse.
Keep posting, it will help.