1. He doesn't have to sign the birth certificate. If he wants to dispute it he will need to get a DNA test done.
2. You just need to give his details to CSA. They will deal with him for you. If he disputes paternity he has to do a DNA test.
3. You can use any last name you like. Your name, his name, a name you happen to like that you found in the phone book. One of my friends has used a traditional Arabic naming whereby his children's family name is Ibn W. Ibn meaning son of.
4. His attitude will not affect your payments. Once child support kicks in that might change the amount because it will be income for you.

I think that you should be more concerned about protecting your child's rights and entitlements and yours too rather than your Ex's. If he wants to be a deadbeat Dad there's no way you can protect him from his own stupidity and deadbeatness.