Aww, hon, I am so sorry that he's being that way. I still stand by that your baby does not get his surname.
But, I am still adamant about the birth certificate and his name being on it. Your child is whom you should be thinking about in that aspect, not the problems you and him are facing.
Do you remember when you had to show your birth certificate for certain things as you were growing up? Perhaps even a project at school? I feel that child will be so embarrassed to know that her father is "unknown." Also remember, this birth certificate follows that child throughout life. I would have been very, very embarrassed had I had that on my BC.
And would you not be embarrassed too when registering your child for school, or whatever, when someone looks at the BC and it says father unknown? Unfortunately, people look at that and then form their own opinion. What would you think if you saw that on someone else's certificate?
Unfortunately, what I would think is that the mom slept around. Sorry to be harsh, but that's my opinion.
Here's another example. What if your child was all alone in the world and god forbid, something happened to you? He/she deserves the right to know who the father is.
Also, say you need to go after him for child support? It makes it a whole bunch easier when his name is on the certificate.
I know you are going through something awful but the future of your child is what matters here. He/she may never know her father. Who knows? Hey, he's only 18 and guys do grow up a lot later than women. He will grow up one day, I assure you.
Sending you big hugs