Should i put my babies father's last name on the birth cerificate?

I am 18 years old and pregnant with twin boys. When i met the father we were in love and despite his immaturity i was able to deal with it. However, ever since he found out i was pregnant, which was 5 to 6 mths ago (i am now a little over 21 wks.) he is constantly going back and forth and contradicting himself. hes threatened to take away my children more times than i can count and not only that i am scared he somehow could because i am not famaliar with legal matters. Also, at one point when he had made me feel like my back was up against the wall I told him I would rather just give my boys up 4 adoption then ever have them be with a father like him and be brought up the wrong way. In response to this he told me that he was going to get one of his distant family members by marriage who is quote "like a mother to him" to give him money to get a lawyer and get the kids himself if i was to put them up 4 adoption. So again he made me feel like he had me cornered.... He has taken off the door handle to my car in fits of rage when i was trying 2 leave, he has also had an incident on the campus i was going to where he had taken off his shirt and threatened to break through my car window if i didn't give back his laptop. My intentions were good and I was going to give it back as soon as he calmed down, and in no way would I have ever kept it but I was to scared to approach him at that exact moment in time and so that was his way of handling it. Now he is telling me things like he loves me and I'm not allowed 2 talk 2 anyone else, and hanging up on me when I start talking about how dissapointed I am in him when he doesn't want to hear it. The other day he had hung up on me and turned off his phone for thirty minutes then turned it back on for an hr and continous like that all day long, on and off, on and off. He says he wants the kids to have his last name but yet he dont even make enough to support one of the twins. He has had oppurtunities ever since he found out to try and find a better job than the local grocery store he is at in beamont texas called kroger. He also just started there after quitting his job at chic fil a after about 2 months of arguing over me telling him 2 get more hours. That was not what i meant though, I wanted him 2 get a job that was higher than minimum wage and wasn't a place where you would find the typical 15 or 16 yr old working. He tells me I complain to much to him and nag to much about getting a job, but honestly i have barely 3 mths left of my pregnancy, the c-section is @ 35 weeks and I'm so worried about how we are going to support the kids that I can't possibly ignore that fact and not mention it in a conversation to him. I just want the best and most easiest life for my children and he has been giving me obstacle that have only gotten worse since we first found out. I do not want to have his name on these children's birth certificate if he can't be there for me emotionally and support me throughtout the pregnancy but would that prevent me from getting child support? I do not want to take away any of his privledges as a father but what do u do when hes demonstrated nothing but unsound behavior. I've tried everything I could to work this out with him so our chiildren will have two birth parents that get along but he just doesn't want to co-operate. And if i ignore him I will be tormented by thoughts of well what is he going to do, or is he talking to a lawyer right now. What should i do? Im lost and I just want the best for my two boys. Does anyone have any suggestions or are famaliar with law?