**** I had t sign a waiver that said they could fire me at anytime with no reason.
That's At-Will Employment, and it doesn't count if they fire you for a discriminatory reason. When they say they can fire you for no reason, that means they can walk in one day and fire you because they just don't like you. But if they give you a reason and that reason violates discrimination laws, you're got them.
In this case, he certainly has a case because courts have determined that alcoholism is a disability that is covered by the ADA. If he can show that they did not offer reasonable accommodations to deal with his disability, he will win, slam dunk. Their defense will have to be that they attempted to work with his disability, but that he could not perform the required duties, even with accommodations.