Wow, even E Jean wanted to kick him in the balls.
I think though she assumes this lady is unconsciously wanting to stay with this man because she hasn't left him yet, I suspect that her staying with him will just end up creating crushing resentment and kill the marriage anyway.
Firstly, he cheated on her.
Secondly, even though she had wanted children, she had loved him enough to choose him over a hypothetical baby. Apparently, he didn't love her enough while cheating on her with a younger woman when he got baby rabies.
Third, who is to say that this younger woman won't want a continued presence in the baby's life if the wife (as suggested by E Jean) should take or adopt the baby to raise? Could this even happen without creating paranoia and resentment in the wife, while allowing heavy temptation for further sexual activity since he happily slept with Side Dish to conceive the baby?
And lastly Fourth, what if this side dish wants this baby to have a sibling? Will the wife even able to stop him from 'helping' this woman make another baby, since he didn't (and wouldn't) listen to her the first time?
So many issues, I suspect this is a dead marriage walking. This man is a slimeball that clearly has no respect or love for his marriage vows, or his wife. If it were me, this man would be gone, he would have irrevocably broken my trust and betrayed me in the worst possible manner.
More then likely the LW's marriage will end in divorce.