Last name opinion

Me and my baby's father are no longer together, we were broken up when I got pregnant as well, we were only talking about getting back together. Things ended up not going forward and we stopped talking all together for maybe 2 months, then I found out I was pregnant and he was the only guy I slept with. He was in a new relationship and at first didn't believe me that it was his, which I get why bc we tried off and on for almost a year (I was young and so in love, I know it wasn't smart) and never succeeded and then when we weren't necessarily trying (still wasn't being safe though) it happened. He didn't really talk to me much for the first month, but came around after a few weeks of us finding out. He was still in a relationship, but talked to me basically everyday. Then he started coming to my dr appointments, and we talked a lot more, basically all day everyday and we talked like we were friends, it wasn't just about the baby anymore. He has a daughter(not from the girl he was dating) and he never sees her bc the mother and him don't get along and she refuses to let him take her. He told me how he doesn't want that with this child and would be here no matter what. He also told me how much it would mean to him if the baby got his last name, I wasn't all for it in the beginning since we weren't together, but I told him as long as he's involved through out my pregnancy and I really feel he'll be constantly involved with our child I don't see it being a problem. Fast forward a few months, him and his gf broke up bc he said he wasn't happy and deep down he knew he wanted to be with me and be a family. So we start hanging out and spending the nights together, basically acting like we're together. This lasted about a month, and then just 2 weeks ago he tells me he's still in love with his ex and can't date me right now. I got pissed because he led me on and it hurt so much, especially bc he always complained about her when they were together and kept saying how happy he was with me. So I kinda said i want to give our son my last name bc I cannot trust him and I don't want him growing up with a last name from a man he barley knows. He flipped out and told me he hates me and he doesn't wanna talk to me until in in labor. I texted him maybe 4 days later trying to get on good terms, but bc I was still saying babys getting my last name, he didn't want to talk to me. He texted me today (a little over a week later) and asked how I'm feeling and now we're just having a normal convo. I feel bad bc he has been there for the majority of my pregnancy, and I don't think he's gonna become a dead beat, but I also don't know how I feel about giving him his last name bc he can get so childish and it's going to make things more complicated on my end, especially if we never end up together and I marry someone else. I'm due in two weeks, and just really stuck. The only problem with my last name is our son would have the name Jayden Smith, and I don't want people thinking I named him after the celebrity. I know it's not that big of a deal but I never thought I'd end up thinking about using my last name, so I never even thought about that lol. Anyways, I'd like to hear from others what they would personally do, I know it's all up to me at the end of the day, but it's nice to hear other people's point of view. Thank you guys and sorry for the book!