Your story portraits a dude who used to cheat on her wife probably with "her consent" because she knew she was dying.
He probably uses his "pain" for losing his wife to get women.
He is going away from you because the last thing he wants is "problems" and you were confronting him too much.
I know a marriage where the husband cheated on her wife. He even had a child with the other woman.
The wife swallowed the incident, which was an out of marriage relationship that lasted years.
The other woman was the one calling to confront the man all the time. The continued confrontations bored the man to the point of stopping his relationship with her.
Up to today, these couple still are married. Slowly but surely the wife won his love back, his interest to keep the family together, and you can tell that they are "happy".
I admire this smart wife, who had patience enough avoiding to be the "problematic wife" and waited until the other woman becoming the "problematic lover".
It is understood that this "method" won't work for everybody, but it did work for the wife of the story.
You want a father for your child, but who knows if your son wants another father. Just think about what you want for you. "Widowers" might not be your best choice.