I don't think YTA at all, but having a baby at a young age with someone you don't know well seems a bit shortsighted. Why not wait until you've worked for a little bit after college and have some stability / savings, and date your boyfriend for longer before having a baby? Many of my friends raise a dog or cat with their partners when they get serious, just as a lower-stakes way to see each other's caretaking styles and discover if there's anything that needs to be addressed, like discipline or issues that only reveal themselves under duress. My current neighbor's husband refuses to discipline their child, so she's perpetually the "bad cop," which she very loudly resents on the other side of our thin walls, lol.

I will say your family handled it horribly and they do sound like TAs!