Baby daddy and his family

So I am currently 9 weeks pregnant. I am so excited and love already. I’m 18, my babies dad is 21. We’ve been together for 2 years. He already has a son that he has most of the time and is very responsible with him. My pregnancy was not planned. We do not live together, I live with my best friend and he lives with his friends mom. The last couple of weeks he’s decided he doesn’t want me at my house because he doesn’t like my friends boyfriend, and has had me sleeping at my moms house, on her couch. I have no problem with this because I love staying with my mom and we were supposed to get an apartment at the end of the month and it was only temporary. Well, things have been really shitty. I found out he has a little side girlfriend because she post pictures with him and is posting about him. I found out because we share a phone plan, I found her number, looked it up and then found her Twitter. I messaged her really nicely asking if she was talking to my bf and she said it was none of my business and I told her I was pregnant and she continued to tell me to leave her alone and that I’m a “stalker.” She tweets about them sleeping together in a bed etc. This really pissed me off because he’s in bed with another bitch while he’s having his pregnant girlfriend of 2 years sleep on a couch? I turned off his phone and haven’t been talking to him since. He started posting about how “no girl can ever ever trap him” and she replied to him saying “stalker bitches lol” I have asked him to give me the money he owes me back because after all I am only 18, I need my money back for my bills and I had to pay for my first appointment due to insurance trouble. He refused. Before all of this happened I let him borrow $200 for his car payment but he promised to give it back. So, I messaged his mom very respectfully. She asked me to call her so I did and she went off on me saying I disrespected her by talking shit on her son. I never called him one name. All I said was I won’t forget the way he is treating me now. I blew it off and apologized to her but she kept threatening me saying “I may dress like a guy and act like a guy but at the end of the day I’m still a female” (she is gay) basically hinting she will beat my ass. THEN his pregnant sister messaged me saying I need to “watch myself” and a whole bunch of shit. My question is should I cut off all ties? Should I let him in the room? Should I give my baby his last name? Let him be on the birth certificate? I’m really lost. At the end of the day this is all petty drama. I wish things were different and I was 30 and pregnant and married because this is so hard. I can support myself but it’s hard doing it alone and I’m not even in my second trimester yet. I’ve been to 2 appointments alone so far while he’s out sticking his penis in some bitch that’s disrespecting me. And his family has some fucking nerve. Should I cut him off completely? He’s telling his little girlfriend it’s not his baby.

The tweets between him and his little girlfriend.

The messages between his mother and I, she then called me and went off on me saying I disrespected her. Also told me him taking my money and not paying me back was none of her business.

His sister messaged me after I apologized for his mom even tho I see nothing wrong with what I said... acting like she’s gonna do something to me when I’m pregnant with her niece or nephew.