If you want to know how it will affect your kids go over to the ACOA forum (Adult children of Alcoholics) and read their stories. Even in homes where the alcoholic is perceived as being calm the chances that your kids will:
1) Become alcoholics or addicts
2) Will marry or become involved with an alcoholic or addict (or many)
Is much higher.
This is not a calm household though, its an abusive one. As Dandy pointed out physical violence does not have to be present to be living in an abusive situation. Your children are being affected by it.
I am very glad to hear that you have family support that is awesome. As for what his family will or won't do for him in a custody hearing put it out of your mind. You can't control that and its future tripping. Yes, make an appointment with an attorney and figure out what you need to do or what a divorce separation will entail. Prepare a plan as the others have stated and as Dandy advised, contact a DV hotline for advice. Its is confidential. I also suggest that if you are using a mutual computer that you erase the history and/or set the cashe so that it will not leave a trail to this site.