Wow. I'm really struck by your statement that you had a wife "who could do no wrong" for the first 4 1/2 years of your marriage...but who stole $40K from your business in the first year of your marriage?
You feel like your job right now is to stand by your wife and support her through her various issues. Let me just share the experience of the many, many, many family members and friends of alcoholics and addicts that have come before you: That's not going to work. The only person that can fix your wife is your wife. If she doesn't want to stop drinking (and/or drugging), she's not going to. No big deal.
In the meantime, you could really use a support system to help you and your kids get through this. I highly recommend Al-Anon. It's a combination of a support group and cheap therapy that a lot of us have found to be really helpful. If that doesn't appeal to you, think about getting a counselor--for yourself--that has experience dealing with addictions. Odds are though, he/she will suggest you try Al-Anon.
This isn't a problem that's going to fix itself. And to the extent that it does get fixed, it will take time. Alcoholism and addictions aren't usually "cured," and relapses are common...especially if the alcoholic/addict isn't fully on board with the program.
Please think about getting help, even it doesn't feel "comfortable."
Oh yeah. One thing you can do immediately? Stop keeping any more money in your wallet or funds in your joint checking account than you can afford to lose.