am i tripping?

i mean are we really surprised he had a kid?

There’s literally so much wrong here I don’t know where to start. Why isn’t the child in school? Can you not privately tell someone?!

Go. To. The. Shelter.
Start afresh.

Immigrant or not, you'll get some form of help as you're with a tiny human.
If you are religious, go to your local church/mosque, they will be more than happy to help you somehow till you find your feet.

Also, is going back to your grandma not an option?

Better there than with someone who clearly just saw you as free childcare for him while he still Carries on with his life and puts yours on hold.

Forget the threats to not marry you and give you papers. Even if you decide to stay in hopes he will do that and sort you out, he could use that and frustrate you even more. Before you know it, you have lost your youth, confidence, time, etc.
Don't let anyone blackmail you into staying in a situation that is draining your life.
Besides, if he's a citizen already, there should be benefits (immigration-wise) for you since you have his kid.
Research for organisations who help women in such situations. I know in the UK they are called "women's aid".

Feel free to chat anyone you trust in confidence. There's always help. You just need to be looking in the right direction.
You are also not in the wrong, if any, it's him. He should even be reported to those in charge to answer for why his kid is not in any form of education.
And why he is using your immigration status to manipulate you because clearly, this is Immigration-abuse.
He doesn't want you being in touch with family as much as you should because he knows they will quickly see through everything and force you out themselves. Doesn't look like he wants to lose the free childcare he gets if he's making threats at each point to keep you from leaving. 😒

Sorry you are having to go through this 🫂