Several things may be going on:
One possibility is that he is going through a transitional phase after stopping drinking ... as mentioned in the post above. When my AH made his first real attempt at sobriety, he attended AA to help him deal with all the cravings, mood swings and anger he was going through. It can take at least 6 months for alcoholics to recover mentally and physically from the effects of alcohol. Many times it requires some type of support group to guide them through the tough times.
Another possibility is that he could be secretly drinking and trying to hide it. When my AH secretly started drinking again, the first major change I noticed was his intense anger and criticism of everything I said or did. He became meaner than I had ever known him to be ... swearing he was not drinking while carefully trying to hide his relapse. It was much easier for him to justify to himself that is was okay to be drinking again ... if he could find someone to blame for his problems other than himself. My father, who was also an alcoholic, normally was easy going, but could become suddenly nasty and provoke a fight when feeling strong cravings, just so he could use the argument as an excuse to stomp out the door and drink. Anger, denial, lying and blame ... are all classic behaviors of alcoholics.
Keep reading the posts both old and new. You have found a wonderful place to learn and understand the struggles families go through while dealing with the very complicated issues of addiction. The more you learn, the more at peace you will feel with your choices.