I don't usually post very much, but my husband left while I was pregnant also. We actually did IVF, and when I was 5 months pregnant (the day before mothers day) dropped the bomb. He moved out a month later.
Some of this MAY resolve when he holds his daughter, but I can tell you it's short lived. My husband moved back home the week after my daughter was born. He stayed two days and left again. He told me had cried the entire week missing her and our son and that he couldn't believe he wasn't the one to take me to the hospital or drive us home. But, once he was actually there he couldn't do it.
I haven't had time to read your whole sitch, but the recent stuff with him saying you aren't "fun" is EXACTLY, almost verbatim actually, what my husband said. After we had our first baby we had fallen into a rut, and I wasn't doing much of anything. I validated him on that point. I wasn't much fun. I became a "mom". I was focused on that and that only. I didn't realize how much of myself I had lost.
Anyway, there is hope. My husband and I are back together and he is moving back in soon. We still have a long road a head of of us though. I should also say that my daughter is almost 18 months old...so this takes a while!