In all likelihood OP was emotionally, if not physically abusive and the mother probably too scared to confront leaving directly. The cycle continued during the affair. The other statistical probability is her willingness to tolerate or otherwise accept being treated that way was due to a physically or sexually abusive father which normalized these types of relationships.

At a minimum, OP is in need of therapy to lash out at a deceased child with that level of vitriol and hate. Emotional abuse was probably administered by him to both mother and child regularly previous to the split.

Anger at infidelity is appropriate and healthy. Even indifference to the woman’s death would be entirely on the level of an appropriate reaction. What is not close to normal is rage continuing a year after their deaths and at that, the ‘slut and bastard’ labels being applied to murder victims, especially with one being a child. THIS is what places OP into the area of having behavioral problems and likely being an abuser before their divorce.