Your situation stinks and you have my sympathy. Raising kids is a challenge and it is even more challenging that they were subjected to an alcoholic. Would they be willing to attend Al-Ateen (if you have meetings in your area) or how about free counseling services? Yep, they're giving you the disrespectful mouth they learned at their daddy's feet. I don't have kids so I will not tell you how to handle this. I'm older than a rock, so I can tell you when I was growing up, kids didn't say much of anything. Period. We got smacked so we kept our mouths shut most of the time. "Wait until your father gets home" still evokes fear in me - and dad passed away in 1994!
When I lived in Maryland, fathers who did not pay court-ordered child support had their wages garnished. How about getting your attorney, or any family law attorney, to petition the court to garnish his pay?