I really think you should start a thread in infideliy. I really think you can benefit from the guys over there.
I'm no expert, but your husband's words, as cruel as they are, are total script. The put downs, the "you need to get over this", the "it was the best thing I ever did, leaving you high, dry, and pregnant" all point to one thing: he's feeling VERY guilty and you're rubbing salt in the wound by telling him how much he's hurt you. He's protecting himself by being nasty to you.
Remember how just a few weeks ago he broke down when you told him that he was right, he never loved you, your 15 years together was a sham, etc.? When your feelings boil to the surface and you tell him how mean and cruel he is, he can't handle it and attacks you to shut you up. If you were a guy, he'd start a fist fight. But since you're his wife, he attacks your emotions and says things that cut you to the quick. Unfortunately, his words do more damage and last longer than a bloody nose or black eye ever would (not that I'm in ANY way condoning physical or domestic violence, but bruises heal; cruel words and thoughtless acts seldom do).
Deep down he knows he's being a monster, but that same monster has control of this thoughts and actions right now. I'm no psychologist, but I honestly think the pregnancy brought on a MLC of epic proportions because it forced him to deal with all that abandonment baggage from his father. He couldn't deal with it, and you and baby grand are paying the price.
My FIL left when WH was 15 and WH spent the next 25 years hating his dad. When FIL came to live near us for six months back in 2005-2006 with his wife to do some volunteer work and get to know his grandchildren, FIL and WH bonded. At the time, I thought it was good that they finally mended that riff. But WH had HATED his dad for SO long that when the older, kinder FIL showed up, it confused WH's inner child. It contradicted all those feelings he'd had about his dad for 25+ years and he couldn't deal with it. End result? He recreated the chaos in his house that he'd known as a kid in his parents' house. THAT he understands, because he already lived it.
I honestly think your WH is doing the same thing. The grown up in him wants to be a good husband and father, which is why you had 15 wonderful years together and he stood by you through the invitro. But he's recreating the chaos from his childhood to deal with the inner turmoil he's feeling right now about being a father. Any challenge to that from you (and probably your inlaws) is being met with cruel and inhuman verbal blows.
You're right: the best thing you can do right now is to excise him from your life. He's toxic and infecting you.
Compartmentalize the emotions, if you can, and put on your business face. Box up his stuff and get it out of the house. Get a separation agreement in place. Make that visitation schedule, even if he doesn't want it. YOU'RE calling the shots right now, not him. He's toxic and infecting you. You're protecting yourself and baby. Let him deal with his demons on his own, away from you.
Have you talked about divorce with him? Does he want that?