I can see where your boyfriend is coming from and I think you're focusing on the wrong thing ("that he knows best" which is not what he said at all per your OP). It goes from sympathy to exasperation over time when you watch your partner hate their job and (I'm inferring here since you seem miserable at your job) listen to them complain about their job. This was the last straw for him -- "just quit your job already if you're miserable and about to leave anyway! why suffer the next 3 weeks?"

I doubt he wants to discuss it further. You made your choice, and he doesn't want to talk about it anymore. I would let it rest and keep doing what you're doing.

One thing to add:

I really appreciated one of my co-workers. I didn't want to make her life harder by quitting before the project finished.

I understand this mentality, but if you are miserable then quit your job. In my experience, coworkers come and go when you/they have to go and there's no harm no foul, just working life.