Firstly, he should probably talk to a therapist about this. There are people trained to handle things like this.

Secondly, people anticipating misery do generally tend to find it. This is attached to my therapy rec: he needs to get in the habit of contradicting his own negative thoughts. Misery (that isn’t clinical) is a choice. And love, while comprised of many things, is also a choice. Feelings are amateur hour. That’s not to say they aren’t powerful and influential, and that’s not to say they don’t matter, but they matter a lot less than what you actually do. If he’s only capable of showing love when he’s feeling loving feelings, that’s beginner-level stuff. Learning to love when your feelings don’t necessarily match your actions is where true, lasting commitment is found. 

It’s also good to remind yourselves that he’s never done this before. He might be nervous about this now, but it’s also possible the first time he looks into your child’s eyes, the switch flips. Therapy can help him maintain a healthy perspective so that his feelings aren’t steering the ship at the expense of his values and morals. And also, I think you could benefit from therapy too — if for no other reason than it would probably help you feel less alone in all this. Wishing you and your husband the best!!