I'm going to try to see this from your H's point of view. He got caught up in this EA, and he starts thinking your M won't last. Then his new soul mate gets ripped from him, and he is told he will be a father, at the same time.
The baby is very real for you right now, but for him (esp. since it is his 1st) it is a very abstract concept, and not an attractive one. Guys can imagine crying babies and smelly diapers and no sex. Imagining that they will love this tiny person so much is more difficult.
He recognizes his responsibility. And so, despite his feelings or lack thereof, he is committing himself to you and the baby for another 10 months. Don't think of it as a deadline, think of it as a minimum guarantee. He has no expectation that it will work out, but he will stick it out for that long.
You can expect the baby to make things much better or much worse between the two of you. He will either step up, and realize the benefits of parenthood, or he will resent every inconvenience and change in his lifestyle. If its the latter, then he will be marking time till May.
I'm certainly not suggesting that you sit idly by and wait for the baby. You two had some kind of problem before the EA, and certainly you need to work on that. Read DR, talk to a coach, get him into MC if you can. Hopefully your R will be on the mend by the time your baby comes.
I just wanted to point out that since the EA was "busted" by OWH, rather than H's choice, he is still grieving that loss. It will take a while before he can be expected to be upbeat and positive about his family.
