I'm going to keep it here because it's a bigger thread... In future, try to keep your posts together, don't post multiple threads because it gets confusing.
First, your son's father should check his rental agreement. Many agreements forbid having guests that stay more than 21 days. So the landlord might be able to tell you to leave, or evict your son's father, for breaching that.
If his agreement *doesn't* have that, and you stay more than 30 days, you might become a "tenant at will" OF YOUR SON'S FATHER. The landlord couldn't kick you out, but your son's father could. And you can bet that the landlord will require him to do that, or will take steps to evict him.
The landlord (or manager) has made their decision, and they're siding with the other tenant. Can you fight it? Sure. It's not likely to end well for your son's father, though.
