My husband knows he is an alcoholic but with all the problems in our lives he thinks its understandable- how can I help him see otherwise?
You may not be able. You may have to figure out how much more you can tolerate of his behavior, if he is not willing to seek help you may need to set some consequences for his continued actions. Alcoholics will drink if the sun comes up, until they admit that they just cannot not drink, everything is a reason to continue. Harsh but true for severe problem drinkers. Talk to a professional or counselor, try alanon.
You really can't. I strongly suggest that you involve yourself in treatment for you, and that other members of the family living in your household may want to as well. Alanon is similar to aa, but is for the loved ones and friends of the alcoholic. People there will help you learn that you are powerless over your so's addiction, but you can help yourself and family by not enabling it. Be loving and supportive.