Sometimes alcoholics who go cold turkey on drinking just switch addictions. It is possible he has been taking pills for the past year or so. It is possible running out of pills caused the anxiety and insomnia. It is possible that today he is mixing pills and alcohol, or just decided alcohol alone is cheaper.
If he is drunk and threatens to hurt you, call the police. Some hours in the drunk tank and a possible RO is a cold dose of reality much-needed by an alcoholic. However, as posted above, if you are at risk please also contact 1-800-799-SAFE for advice about how to best deal with a potentially violent husband.
If he seems incredibly ill, you can call 911 for an ambulance. Again, cold dose of reality, and it relieves you of any responsibility for his physical safety.
Relapse is vicious. If you have a friend or family member who can shelter you, I strongly suggest you leave now for a long visit with that person and take a couple weeks minimum to organize your thoughts and make plans, away from the insanity of your AH. He really won't care if you're gone. He may call and try to harass you. But really he'll be glad you're gone.
You CANNOT talk him out of drinking. Tears, threats, silence, nothing will work.
He is back on the rollercoaster and you can choose to ride it or not. We very much hope you don't. Boundaries make all the difference.