First and foremost, I agree with what other have said about enjoying what you have.
At the same time I would not give up $2K of monthly side hustle money for more space for a baby. I guess living in 600 SF with 4 people is tough too. Could you add on a porch, little more outside living space cover it, screen it in, put a fan out there, area rug, some outdoor couches, a screened gazebo/play house? That could add value and would pay for itself relatively quickly at $2K/month.