Hello,
Alcoholics drink (and hide alcohol and lie about it) because they have an uncontrollable mental compulsion to drink and an uncompromising physical dependence on alcohol. It is not a victory to catch them in the act or to find their booze. It's easy. They will be doing those things like the sun will be coming up in the morning. This is alcoholism. The neurology of the brain has been altered. And the physiology of the body has been changed.
Your anger and resentment hurts you and it hurts your children. Believe it or not, some children from alcoholic families reach adulthood and feel more bitterness toward the sober parent than the drinking one. Your therapist could talk with you about the reasons why.
I think Al-Anon meetings can help you. You can find a different meeting. You do not at all have to reveal your use of medical marijuana. It is irrelevant. Al-Anon is a program for spiritual development designed to help us stop playing God. Its primary purpose is to help families of alcoholics accept that which they cannot change and to turn their attention to their inner life. As we get more in touch with who we are, we find we are better able to know what we want and how to achieve it in a sane and measured way. Your main focus right now is figuring out how to ambush the alcoholic. Al-Anon can re-direct your focus.
Somewhere within all this chaos you are living is YOU. And your life path, your calling, your unique unfolding.
So, I would find a meeting and attend weekly. I would continue therapy. I would separate from the alcoholic if I could not remain sane and centered while living with him.
I did all those things years ago, it worked for me. And fear melted away. No longer did I have to be afraid of what would happen next.