Honestly man you need to get her to get that abortion. I got friends who have kids with stupid bitches, not one of them is happy, not one of them has custody of their kids like they should, not one of them is anything but miserable in that situation. I also have female friends who are single moms and the reverse where they have some piece of shit ex who doesn't give a fuck.
At least you are willing to man up in the situation, if you are serious about it and the abortion is out of the question you should attempt to get custody and start setting yourself up for that situation. Sounds like this chick will be a horrible parent and the kid will grow up fucked up if she raises him. Do the world a favor and get that second job, stack cash, get off paperwork if you are on any and once she has the kids start filing paperwork for custody.
But seriously man, you need to find a way to make that chick get an abortion. If you don't expect to spend a long time dealing with her drama on a constant basis. If this is any indication of the level of stupid childish bullshit you have to deal with you can only expect it to get worse and you got to understand you got permanent ties that chick from this. It's not gonna be a situation where you can just stop talking to her one day, or you can just delete her from your life, unless you want to delete you child from your life as well. Also I would suspect that she is the kind of woman who will poison your child against you, making your child grow up with animosity towards you and some serious life long issues they might need therapy for.
Of course you could always take a cue from