Oh, dear, I am really sorry you are going through this. How disappointing.
I think there is a big gap between allowing him to stay in your home and never seeing or talking to him again. It was easy for me to go No Contact with my XABF, we had no children together. But you don't have to let him stay with you. It is his responsibility to build a life that can include your son.
But it sounds to me like you are more still missing the relationship and hoping things would be different, and I get that. There is only one way past that, I'm afraid, and that's accepting him for exactly who he is right now, bad and good, and making decisions based on what you know, not what you wish for. Hugs to you. It's a sad place to be. Lots of folks here to listen.