You describe your partner as a "violent, drug using criminal." But the sense I have from your email is that's a general description of his past acts, not necessarily how he is right this minute. So the first part of my suggestion is treating your situation as if your partner is not currently using and/or violent. The second part will address if he is currently in that state.
The answer is Faith.
But Faith without works is, as they say, dead, so let's also consider some works which might help.
My own experience with fear is that the less information I have the easier it is for me to be paralyzed by fear -- that is, if I have some facts, or likely outcomes or whatever, then when I'm afraid I can measure my fear against the information I have, and begin to put it in context. This helps me to either get a plan or stay in action (or most likely a little of both). What that might mean in your case is to begin to get some one-on-one legal counseling. The book "Alcoholics Anonymous" suggests we make good use of the professionals around us, and if you are contemplating a divorce, especially when there is a child involved -- or if you are not married but there will be issues of child support, custody and visitation -- you need sound legal advice. Legal counsel generally costs money, but there are some agencies which might at least give you some general guidance for free or at low cost. Googling the phrase "free legal counsel for women" gave me a return of 5,570,000 results. Plenty of that might be crap, but it's likely there are services available near you to give you some info. Once you have some information, you can address your fears as either realistic or unrealistic (from your email I can tell you have a great grasp of the fact that we are tortured by both, and that sorting them out is a wise course). And when you can view them as either reality or fantasy-based then the application of faith (prayer, writing, meditating) can be maybe more focused and thus more effective.
Sounds to me like you are fairly active and involved in the 12 Step world with two different programs which are well suited to what you are facing -- both within and without. I encourage you to lean into them, and if you haven't, find a sponsor in at least one of them to help apply their solutions to your situation.
Also, your self-diagnosis is very wise. Some of what is keeping you stuck involves issues of self-esteem, fears of being alone, etc. Inventory work and service will help with much of that, but also a one-on-one therapist/counselor is probably in order.
The Big Book specifically suggests writing about our Fears before we pray about them, and that has always been powerful medicine for me to apply. Writing them out and then praying about them can bring some immediate relief -- and with the relief can come the ability to take action and move on.
Finally (for this first part), remember that this will be a process. A messy, ambling, back-and-forth process, with some progress and then some backsliding. This is a complex situation given that you have a child and you have been involved in this relationship for more than a decade. You sound smart enough to know that while you are aware that there is a lot going on you also understand that there is even more going on with you, with him, with the whole deal, than you can perceive. Given that insight, for the sake of your sanity and your child's mental and emotional health do not let the idea that there is "no light at the end of the tunnel" define you. Many small changes and a hundred little insights can add up to a whole new perspective and ability to change -- or in your case, leave. (Or stay, but be at peace. Whichever is right for you).
Now, the second part of my answer, if your description of your partner is one in which he is currently either violent -- or potentially violent -- while currently drinking/using:
1. I will not cluck my tongue and wring my hands and moan at you to wake up and realize the danger you are in. People in abusive relationships have a kind of blindness and paralysis that are no simple things to break through. But please try and admit to yourself that you are indeed in an abusive relationship -- a full on, Lifetime TV Movie abusive relationship and those are sad stories for good reason. Your safety and the safety of your child is at grave risk. You are trapped in a cycle and while you can do a lot on your own, you will do better if you get outside help to safely break free and stay free.
2. Yes, it is highly likely that your partner will "turn on you" in some way or another when you leave. If he is a violent man you are right to be afraid -- that is your survival instinct talking and I hope you keep listening to it. I am not a professional counselor, but I do know that in such a situation you need a specific plan, outside help and support before you take your child and go. A mad dash out the door in the middle of the night might save you from immediate harm (and sometimes that's the immediate goal) but does not help you stay away. Do not minimize your situation. Call this number: 800-799-SAFE or go to this website: http://www.thehotline.org/get-help/help-in-your-area/ for people who are a lot smarter and more experienced than I am with a situation like yours. REMEMBER: computer histories can be recovered. If you fear that he is checking your browser history or monitoring your computer use it might be better to phone the number than visit the site at first. Only you can judge which is right and safe for you. Do not delay. Do not listen to any voice inside you which suggests you wait to take action.
3. Fearful, it was hard to judge from your email exactly how much, if any, immediate danger you are in -- your "voice" seemed very recovery focused, and not like that of someone at risk as they wrote. But again I say, DO NOT MINIMIZE YOUR SITUATION. That is how people wind up staying past the point of safety.
If the addict you're addicted to is not going to become violent towards you or your child, and that characterization reflects his behavior in the past, you are right to want to be free and to work with both 12 Step tools to overcome your fear and to work with professionals to learn about cycles of abuse and how you are long-term stuck -- I am certain that there IS hope for you to make changes -- I have seen many people make whole new lives for themselves after many years of addiction -- regardless of how afraid they are, or what (or who) they're addicted to.
If the addict you're addicted to is more immediately combustible then I hope you contact the agencies above and begin to immediately take action to save both the life of your child and yourself.
Either way, you are in my prayers.
Good luck and God speed.