Is there someone from home that can come stay with you for awhile for emotional support? That would be my first priority. Make sure they know what's going on with you and what's at stake. You really, really aren't alone.
If not, I highly recommend getting close with some folks at Al-Anon. They can help you through this time, processing your feelings about the relationship and helping you formulate new plans. Chicago should have a huge network.
A lot of this depends on your A, whether he gets moody and violent, and/or how you feel and what you can live with without going insane. Having a good support system would be helpful. Perhaps consider going home to Oregon shortly after the baby is born.
I was pregnant last year while my RAH was going through the worst times of his alcoholism and trying to quit. He relapsed three times and lost two jobs over the course of my pregnancy, would disappear for weeks at a time, steal money, so much. It's awful to think about. He ended up pulling it together, but that's another story.
At the time, I knew that if he continued to drink (like, life decision) that I would leave. But I needed him, his company (what I had of it) and his income during that time, and I made the decision to stick with it until I was in a better place to make the big decision about whether to stay or go. So one of my boundaries was that I took over finances and budget altogether. If you have control over your own paycheck, I would do that. Not to be vindictive or teach him a lesson, but to protect yourself financially. If I thought he'd been drinking, he couldn't stay at our house. He respected this without a lot of drama (it gave him permission to hole up somewhere and wallow in booze, for one) but it meant that I had to be cool with him being "missing" indefinitely. Eventually, I WAS.
I would really take this time to focus on yourself and what you need. You might want him in the delivery room -- you might find out later that he was kind of useless in the delivery room, like mine was -- but not if he's been drinking. So much of this is fungible. It's okay to rewrite your stated boundaries if they're not going to work. Just have the big picture -- your safety, your sanity, your child's safety -- in mind.
Good luck to you. This is so difficult. I did it, other women have done it, you can do it. You will find reserves of strength you didn't know you had. Bless you, mama.