criminal defense 2nd degree assult

You can't predict an outcome from a short statement; plus there are LOTS of variables like: the Judge, the prosecutor, and (most importantly) the Jury. You have raised some interesting issues though. Your husband faces potential enhancement charges by using a gun, not to mention having a gun on his person when he was not licensed to do so.
Self Defense is a valid defense, though it is not an easy defense. One important consideration is whether there are any witnesses who will testify that your husband was having to defend himself. Next, the reasonableness of using a gun comes into play. The general rule is that you are only allowed to use that amount of force which is necessary to prevent the harm that is being attempted (which means you can't shoot someone for slapping you ... there has to be proportionality). In Washington, there is a concept of "imperfect self-defense" which comes into play when someone uses more force than is reasonable or necessary.
The alcohol is a two-edged sword, the law in Washington is that voluntary intoxication does not excuse a person's actions. It can be played by a prosecutor to show that he did not have control of himself, and by virtue of the fact that he drank to being drunk he demonstrates that he does not try to use moderation, etc. But, on the flip side, the fact that the officers did not draw his blood for a blood alcohol test when they could not have him use the breathalyzer shows a potential weak spot for the police: were they in such a rush to judgment that they failed to do those things a reasonable officer would have done, were they lazy, etc.
Your husband is, unfortunately in a difficult position. Proper work by his defense attorney can lead to a more favorable outcome. Depending on his criminal history, a conviction could lead to substantial prison time ... but if this is a first offense, he may qualify for first-time offender sentence which only requires 90 days in local jail. The outcome has not been determined, it will only be determined after some hard work by his attorney.

Good Luck.

I do agree with the previous answer, there is nowhere near enough information here to speculate about the outcome. The level of alcohol is usually a small part of a case like this; the facts surrounding the argument are far more important.
If he hasn't already, your husband needs to talk to an attorney immediately. Many do free initial consultations, meet with a few and pick someone you can trust, who will do a good job for you. There are a variety of ways to defend this type of case, and different attorneys might recommend different strategies. Remember that the outcome of this case can effect the rest of his life, so don't make any decisions without being fully informed.

You say your husband didn't have a license for the gun. Was he carrying a concealed weapon? That can be a separate crime. If he bought the gun legally, presumably he bought the gun for protection. If you think alcohol is an issue for your husband, you should stress the inherent danger in him carrying a gun around when he's drunk. In Wisconsin, it is against the law to be in possession of a firearm while intoxicated.