All I can say is if you guys cant even agree now, WOW are you in for a long 18 years. He cant make you name the child something that you agreed to. You could have agreed to John jacob jinglehimer-smith. When the child is born you can put RuPaul mohammid Jinglehimer and cut out the husbands part. You can bet he will take it to court and prob get Smith on there.
If you are legally married he doesnt have to sign the BC he is the father. My husband now had the same issue with his ex wife. They agreed on a name and he left the hospital for the night. When he came back the next day the BC was filled out with a COMPLETLY different name. They were naming the son a D name follwed with my husbands Uncles name and his last name. The child was named after her brother with a T name a totally different middle name and same last name. But as they couldnt compromise then they cant agree on the sky color now. Hang on for a long ride!