The short answer is, if DH can't handle the stress of a baby, he needs to change himself so that he can. It's not something you can do for him. Once the baby is born, your first priority will be caring for your baby, not shielding your DH from the stress of his life.
Are you currently pregnant? If not, you have a lot more time to deal with the challenges you are facing. But I assume since you're posting here, that you are pregnant. I hate to tell you this, but I agree with you - having the baby will not make anything less stressful. In fact, it may be the most stressful thing you guys will ever go through as a family, at least to this point. But there is definitely hope. Your best options are to try and address all of your issues now before the baby gets here. Licensed marriage counselors and individual therapy would be a good place to start. There are usually low/no-cost options available through churches, or as a community resource if cost is an issue. Al-anon meetings might also be helpful for you both.
My husband and I had some really heavy challenges too, and the way we got through them was deciding first off that we were a team, and that whatever challenges we had, we would face them together. We decided we didn't want to spend the rest of our lives unhappy, and that each others' happiness was a priority for us. I didn't think there were many issues in our marriage, or that they were that bad, but when he told me he was so unhappy he was thinking of leaving me, I realized that if he wasn't happy, I wasn't happy either. I had no idea he was so upset about a lot of things until he told me. So I agreed to counseling. Best decision we ever made. Our commitment to work through our challenges like the counselor suggested saved our marriage. We are so much happier with each other and at peace now in our relationship. Without this basis, I think the birth of our son would have been much more stressful and difficult than it was. But because we are on the same page now on almost everything, it's easier for us both to remain calm and meet each others' needs while at the same time caring for our baby.
Not sure exactly what you're looking for as a result of your post. But I can say that raising a baby in a home with someone who drinks so much that he passes out and has anger issues is putting your and the baby's safety in danger. My husband had anger issues too, that I didn't know about until after we were married. The first year was so bad, that I drew the line in the sand, and said basically that "if you don't get it together, I'm done". Each year since has been better. He's done a lot of work so that his rage no longer controls his behavior, and he is now able to deal with it in a constructive manner. I've changed a lot too, to help him, I think.
But if we had had a child that first year, I would at a minimum have moved out. Screaming fits of rage and throwing things, punching things, etc. around our child are simply unacceptable. And if he had ever hit me, the marriage would have been over right then. You get what you tolerate. There are a lot of community resources that can help you if you don't have much support from family or friends.
You may have some difficult decisions to make depending on what your husband chooses to do and chooses not to do. But remember, these things are his own choices. You can't make his choices for him, and you can't make him choose more wisely. I know how it feels to wish so hard that you could. If he chooses to drink, that is his decision. He may be upset at you or feel anger at you, or be overwhelmed by you, but you do not cause him to do anything, including drink. He chooses to drink to try and deal with the situations in his life that he doesn't like or feels powerless about, which may or may not have much to do with you. He could just as easily choose to not drink, but to go to counseling instead. (There's the addiction issue which I'm not addressing here, but do you see what I mean about him having ultimate responsibility for how he chooses to deal with situations in his own life?) You can be as supportive as possible, and point him in the direction of good things to do and good choices to make, but ultimately it's his responsibility to change. (You may need to change too, don't forget. It usually takes two to make a marriage miserable.)
Decide what you are willing to accept from him as far as his behavior and commitment to your family. Have concrete consequences assigned if he does not meet your minimum requirements for behavior. Share these with him lovingly but firmly, and be clear and definite about it. (for instance, if you say"I will move out by such and such date if I do not see such and such changes", then do it.) Make sure you address short term as well as long term goals. Ask him if he would be willing to accept and work towards the goals you have for his behavior. Maybe you could come up with goals for his behavior together, if he recognizes how much of a problem it is. Ask him what he would like from you to help him accomplish these healthy goals, and then commit to provide that to him. Ask him what goals he would have for you as far as behavior goes, and then commit to meet them.
Do your best to support him, stress that you love him, but if he does not change his behavior, make sure you take action to protect yourself and your baby.
I wish you loads of luck, comfort, and understanding as you work through these challenges.