An excellent movie- I see a lot of gender Dynamics at play here from a male's perspective.
"Alpha seed/ Beta need" even though she more than likely made more than him, the way she got excited to see Bobby Ontario at the liquor store and then lied about the encounter to her husband.
The law of propinquity at work with her doctor.
Briffaults Law, of wanting to end the marriage despite everything he's done.
Solipsism: He was an excellent step-dad in the immediate proximity of the child's life.